1. Selection and maintenance of poinsettia

1. Buy flowers    

1. Count the flower heads: Each single branch is called a flower head. Generally, flowers with less than 6 flower heads are inferior flowers, flowers with 6 to 8 flower heads are medium flowers, and flowers with more than 8 flower heads are superior flowers.

2. Flat flower heads: The ideal poinsettia should have flower heads of uniform size, evenly distributed on a spherical surface, densely clustered together, with a crown height ratio greater than 1.0 , preferably greater than 1.3  . Such finished flowers look generous and stretched.

3. Look at the bottom leaves: Hold up the poinsettia and look at its bottom leaves from the side. If many leaves turn yellow and fall off, it is a low-quality potted flower. Whether the branches are thick is also an important criterion for judging the quality of poinsettia. If the branches are too long, the internodes are too long, and the branches are completely exposed when viewed from the side, it is also a low-quality product.

4. Look at the flowers: Poinsettia is very beautiful, but it is not the flowers that please your eyes, but its bracts. However, checking the real flowers at the top can help you judge the quality of the poinsettia. If most of the small yellow flowers at the top have bloomed, and there are also many small flowers on the side buds, this is "overblown". Most of these poinsettias have a short flowering period, and it is difficult to extend the display time after you buy them home.

5. Hands-on: Gently fiddle with the corolla. If it is limp, the flowering period will not be long. The ideal poinsettia should have relatively firm branches and leaves, giving people a vigorous and upward feeling.

    2. Maintenance    

1. Temperature    

Poinsettia is native to Mexico and prefers warm environmental conditions (15 ℃ to 25 ℃ ) . However, when the bracts turn completely red, the growth temperature needs to be lowered to 13 ℃ to 18 ℃ to deepen the color of the bracts. Generally, the temperature of 12 ℃ to 18 ℃ is conducive to extending the display period of poinsettia and maintaining the color of the bracts.

In a low temperature environment, the normal metabolism of poinsettia basically stops.

At this time, the poinsettia has poor adaptability, so it should be placed in a relatively balanced and stable environment as much as possible. The temperature cannot fluctuate, especially a pot of poinsettia that has been in a low temperature environment for a long time cannot be suddenly transferred to a high temperature environment, and such a poinsettia cannot be exposed to strong sunlight suddenly. When the temperature is too low, the red bracts are easy to turn into ugly cyan or white. But for the open poinsettia, it can be maintained very well in an environment of 8 ℃ to 12 ℃.

In an environment with excessively high temperatures, the metabolism of poinsettia is enhanced. If there are no suitable lighting conditions, the leaves, bracts, and flower buds will fall off.

    2. Lighting    

Under natural light conditions, the color of poinsettia bracts is very bright and shiny. However, in flower markets or hotels, homes and other places, poinsettias are often rarely exposed to light or are exposed to light for a very short time. Poinsettias need light energy to maintain their normal growth both before and after flowering. Most varieties currently sold on the market require a minimum light intensity of between 800 lux and 1000 lux, and the light duration should not be less than 8 hours.

Generally speaking, the light intensity in the home is only 500 lux to 800 lux, which cannot meet the minimum requirement for poinsettia to maintain growth. This is also the reason why many consumers can only enjoy the flowers for 2 hours after buying them.

The reason why the poinsettia may only last for 2 weeks or even less than 2 weeks. You may want to place the poinsettia in a bright place such as near a windowsill during the day so that it can receive more light, but not direct sunlight. The red light emitted by incandescent lamps can enhance the color of the poinsettia bracts. White fluorescent lamps not only make the poinsettia bracts dull, but the blue light they emit will also cause the red bracts to fade. Therefore, if you want the poinsettia to show a better viewing effect, it is best to use an incandescent lamp with sufficient wattage.

    3. Watering    

Watering is an important part of poinsettia maintenance and management after flowering.

After the bracts of the poinsettia have completely changed color, the overall metabolism has been significantly weakened, and the requirements for light, temperature, fertilizer, and water have been significantly reduced. The correct way to water is to wait until the substrate becomes dry ( the degree of dryness is before the leaves droop ) , and water in small amounts. The amount of watering should just moisten the substrate, not too much. If you can't master it well, you might as well stick to the principle of less rather than more, because even when the water is controlled very strongly, the lower leaves often turn yellow and fall off, while the bracts remain upright. The roots of the poinsettia are prone to rot and are easily infected with gray mold if they are in an overly wet soil environment for a long time.

Another point to note is that when watering in winter, the water temperature must be close to the ambient temperature. Too cold water will cause the poinsettia to "catch a cold", damage the root system, and cause the leaves to fall off. (Chen Haiyun)

2. Key points for poinsettia management

 1. Fertilization:

Poinsettia likes fertilizer and needs more nitrogen fertilizer during the growth period. You can apply decomposed manure liquid fertilizer 2 to 3 times a month. It is best to apply thin fertilizer frequently. In rainy days in summer, it is better to apply dry manure or decomposed sauce residue. Within 1 month after pinching, apply fully decomposed light cake fertilizer water once a week. Before the plant enters the room in late October , you can add nitrogen fertilizer once . When it is close to flowering, it is advisable to apply superphosphate or nitric phosphate aqueous solution once to make the bracts bright in color.

2. Watering:

In spring, when new leaves sprout, less water is needed, and watering is generally done once a day. In summer, when the temperature is high and the branches and leaves are lush, the plant needs more water, and watering is done once in the morning and evening every day. If there is insufficient water, the leaves will curl and wither. After the beginning of autumn, water once a day in the morning or afternoon . Before the plant is established, control the water to prevent the internodes from elongating and affecting the plant shape.

3. Pinching:

After the cuttings have taken root, they should be topped off after about a month of growth, leaving 4 to 5 leaves from the base, and the branch tips should be cut off to promote side branches. 3-4 side branches will grow in the same year. As perennial old branches, 1 to 2 buds should be left at the base of each side branch, and all the upper branches should be cut off to concentrate nutrients and promote the healthy growth of new branches.

4. Braiding:

In August , we began shaping, tying and bending the branches twice. The first time, we twisted the upright branches and pulled them down, and tied them with string to make the plants shorter. The second time, we leveled the tops of the branches.

5. Soil:

Poinsettia likes acidic sandy soil, and the most suitable pH value is 5.5 to 6. Avoid alkalinization of the potting soil. During the growing period, you can combine watering and fertilizing once a week, and water with alum fertilizer.

6. Temperature:

Cutting propagation is best done at 15 to 20 degrees Celsius. The optimum growth temperature is 16 to 25 degrees Celsius from April to October and 13 to 16 degrees Celsius from November to the following March . In winter, the room temperature should be kept at around 15 degrees Celsius at night and should not be lower than 5 degrees Celsius. The room temperature should be around 12 degrees Celsius to extend the viewing time.

7. Lighting:

Poinsettia likes a warm, humid, sunny environment. In May , the plant is moved out of the house and placed in a sunny and well-ventilated place for maintenance. In summer, avoid direct sunlight. You need to build a shed, water the land in the shed frequently, and increase the air humidity.

3. Commercial production technology of potted poinsettia

Poinsettia is an evergreen or semi-evergreen shrub of the genus Euphorbia, also known as ivory red, old tender, and fishy wood. The flowering period coincides with Christmas, so it is also called "Christmas red". Poinsettia blooms in winter, and the flowering period is from December to March of the following year, which coincides with Christmas, New Year's Day, Valentine's Day and the Spring Festival. Therefore, it is one of the most important winter festival potted flowers in the world. Poinsettia potted flowers are brightly colored, have a long viewing period, and have a large market demand. They are perennial, have a short production cycle, and have considerable commercial cultivation benefits.

    1. Ecological habits:    

Poinsettia is native to tropical areas such as southern Mexico and Central America. It likes warm and humid climates, has low cold resistance and is not frost-resistant. It requires a temperature above 15 °C in winter, otherwise it will easily shed its leaves. It likes a sunny environment and is not shade-tolerant. It is a short-day plant and can only bloom when the sunshine is less than 10 hours . It is best cultivated in slightly acidic ( pH 6 ) , fertile, moist, and well-drained sandy loam.

    2. Cultivated Varieties:

There are mainly four types:

 1. Double Poinsettia:

When in bloom, the upper leaves are red, and the petals of the inflorescence are partially transformed into bracts. This is the main cultivated variety. Recently, a new type of double-petaled building has appeared, with well-developed small leaves in the center, towering high, and small flowers that can bloom. The petals are larger than those of ordinary varieties, and the flower colors are the same in red, yellow, and white.

2. Yipinbai:

When flowering, the upper leaves turn milky white. 3. Pink: When flowering, the bracts turn light red. 4. Yellow: When flowering, the upper and middle leaves turn light yellow. 3. Propagation technology: mainly cuttings, root cuttings can also be used for propagation.

1. Cutting time: Using greenhouses and plastic greenhouses, it can be done in late March . It is best to do cuttings in the open field from late April to early June .    

2. Cutting medium: mainly fine sand, perlite, peat, and decomposed sawdust, fine coal slag ash and fine garden soil can also be used according to local conditions. 0.1% potassium permanganate solution can be sprayed for disinfection.

3. Cuttings treatment: Cut short and strong one-year-old branches or new shoots from the mother plant, cut into 5-10cm long cuttings, cut off half of the leaves, wash the cut wound lotion in clean water. Then soak the stem base in 1000 × 10-6 naphthaleneacetic acid for 3-5s , and then cut.

4. Cuttings: First use a small wooden stick to make cutting holes on the substrate, the depth of which is 1/2 of the cuttings , the spacing is 4cm , and the row spacing is 5-6cm . Then insert the cuttings into the holes, press lightly around the base, compact the substrate, and water thoroughly.

5. Management after transplanting: The ambient temperature should be kept at around 20 ℃, shade should be provided with a sunshade net, and water should be sprayed frequently to keep the air and the transplanting bed moist, but be careful not to make the seedlings too wet. It usually takes 20-30 days for the roots to grow after transplanting. When the new branches are 10-12cm high , they can be potted.

To increase the amount of reproduction, root cuttings can also be used. The method is: when repotting and cutting roots in March or April in spring, collect the old roots with a root diameter of more than 0.5 cm and cut them into 7-10 cm long root segments. When inserting, tilt it to about 80 degrees to the north, leaving 1 cm of the root segment above the soil surface , and it will become a seedling in about 1 month.

4. Cultivation and management:    

1. Potting: The potting soil formula is 4-5 parts of compost soil, leaf humus, charcoal soil or wood humus, 3-4 parts of garden soil and 1-2 parts of sand, charcoal slag or vermiculite. For commercial cultivation, ab260 -type white plastic pots are often used. A layer of coarse charcoal slag is placed at the bottom of the pot, and then a layer of culture soil is filled in. Then the seedlings are placed in the appropriate position in the center of the pot mouth, and the culture soil is filled in and pressed by hand. After potting, water thoroughly and place under a shade net for one week. Then grow under full light.

2. Fertilizer and water management: When watering, pay attention to the appropriate degree of dryness and wetness to prevent excessive dryness or wetness, which will cause the leaves to turn yellow and fall off. Generally, water twice a day in the morning and evening in midsummer, and reduce the amount of watering in other seasons accordingly. Drain the water in the pot in time during the rainy season to prevent root rot. Fertilization does not need to be too frequent at ordinary times. Generally, fertilizer and water are applied 2-3 times a month during the growing season. In order to prevent excessive growth, nitrogen fertilizer should not be applied too much. Increase the number of fertilizations and the amount of phosphorus fertilizer at a high level in autumn to promote the formation of flower buds.

3. Dwarfing and shaping: The stems of poinsettia grow upright, without branches that are open. The plants are tall, up to 1-2 meters . If they are allowed to grow naturally, their ornamental value is low. Therefore, in commercial cultivation, they must be dwarfed and shaped to achieve a full, dwarfed and beautiful effect. The specific methods include pinching, pulling branches, pinching stems and tying them together.

( 1 ) Pinching: Pinching should be done 1-2 times during the growth period depending on the branching and growth of the seedlings to promote the growth of side branches. When the plant is 30 cm tall , the top should be cut off. The first-level side branches should retain 1-2 buds at the bottom and the upper part should be cut off. Generally, 6-10 buds should be retained on the whole plant , and all other new buds should be removed.

( 2 ) Branch pulling and coiling: In August and September , the new shoots can be bent once every 10-20 cm of growth until the bracts are colored. When pulling the branches, tie them with a thin rope and pull them to the same level or slightly lower than their attachment points. The bottom 3-4 side branches should be pulled to the same level, and the remaining side branches should be pulled evenly in all directions, with weak branches in the center and strong branches around, with each branch coiled in the same direction. To prevent the branches from breaking, water control should be performed before bending or the branches should be bent in the afternoon when there is less water.

( 3 ) Pinching the stems and tying them: This is another method of tying them. When the branches of the poinsettia grow to 30-40 cm , before they become woody, continuously flatten the branches from the base to the outside in a clockwise direction until they droop naturally. The plants should be in a spiral shape after treatment. Tying them should be done when the flowering period is determined or when buds appear.

5. Late greenhouse maintenance:

Before the cold snap in late October , put the plants in a plastic greenhouse or a warm place for maintenance in time to prevent frost damage. Putting them in too early will cause the plants to grow too tall. When placing them indoors, keep a certain distance between the pots to facilitate ventilation. Prevent the plants from being too close together, poorly ventilated, and too high humidity from causing fungal reproduction, causing gray mold and brown spot disease, and causing leaf fall or flower rot. Too low a temperature will also cause leaf fall, so management should be strengthened.

6. Flowering period regulation:    

1. Heating to promote flowering:

Poinsettia forms flower buds in the open field in mid -October . After being moved into the greenhouse in late October , the daytime temperature is maintained at 20-25 ℃ and the night temperature is 15 ℃. It will start to bloom in early December .

    2. Short-day flowering:

Under the temperature of 20-25 ℃, after shading and 9 hours of light per day, single-petal varieties can bloom in 45-55 days, and double-petal varieties can bloom in 55-65 days. If shading is started from early August , ventilation and cooling are carried out at night, and topdressing is applied once a week , the top leaves will begin to change color in late September and can be put on the market during the National Day.

    3. Long-day flowering:

In order to achieve the purpose of inhibiting flowering and delaying the flowering period, artificial light supplementation can be used in the evening to extend the daylight to 16 hours , or light supplementation can be used at night for 2-4 hours as a dark interruption treatment. 40 × 10-6 gibberellin treatment can also be used to delay the flowering period.

7. Management of finished potted flowers:    

1. Listing standards: Poinsettia plants can be put on the market when they are well formed in the pot and the flowers or bracts begin to show color. The quality requirements for commercial potted poinsettias are: dense and full branches, plant height of about 35 cm , uniform height, and neat and beautiful flowering.

2. Storage and transportation: In order to reduce the bending of leaves and bracts during storage and transportation, packaging can be carried out. 3-4 hours before transportation , pack the plants in porous paper or glass paper, and unpack them immediately after arriving at the destination to prevent ethylene from accumulating inside and causing damage. The transportation time after packaging should not exceed 48 hours .

3. Maintenance of finished potted flowers: After flowering, the finished potted poinsettia should be placed in a bright environment and the temperature should be kept at 18-25 ℃. If the temperature is lower than 10 ℃, the bracts will turn blue and the leaves will fall. And maintain a high air humidity. Watering should be appropriate. Too much watering will easily cause root rot. Continuous illumination with incandescent lamps can extend the life of colored bracts or flowers. Spraying with 0.3-0.8mmol concentration of STS solution can prevent plant wilting caused by ethylene.

( Information source : Xinnong Online )          

4. Pre-harvest management of poinsettia

[ Sunflower ]euphorbia pulcherrima willd ．ex klotzsch   

 [ Other Chinese names ] Lao Lai Jiao, Euphorbia mellifera, Euphorbia mellifera, Christmas red, Christmas flower, Christmas tree, Sunflower, Ivory red, Poinsettia, Red hibiscus, and a little red                              

[ Family ] Euphorbiaceae Euphorbia                                    

[ Origin ] Mexico                              

[ Gardening Features ] Poinsettia blooms at Christmas time, so it is quite popular among people in Western countries. Poinsettia is also widely planted in China. Because it is afraid of cold, special attention should be paid to ensure that the ambient temperature does not drop below 15 ℃ during winter and spring management. 

 [ Pre-harvest management ] The placement density is 4 to 8 pots per square meter . Poinsettia prefers a slightly moist and dry soil environment, and is also slightly drought-tolerant. In addition to applying a small amount of horseshoe slices as basal fertilizer at the base of the flowerpot during planting, a thin liquid fertilizer should be applied once a week during the vigorous growth season. Poinsettia likes a strong sunny environment with abundant sunlight. If possible, it is best to ensure full sunlight. Pay special attention to ventilation when the temperature is low, because the leaves of the plant are prone to fall off when it is directly blown by cold wind. Poinsettia likes high temperatures and is afraid of low temperatures. The suitable temperature for growth is 25 to 35 ℃, and the overwintering temperature should not be lower than 15 ℃, otherwise the leaves will easily fall off, and even cause the death of the plant.

5. Simple dwarfing method for poinsettia

If common poinsettia is allowed to grow naturally, the plant height can reach more than 2 meters. To increase its ornamental value, the flower pot can be tilted sideways to control the height of the branches.

The specific method is to plant the poinsettia seedlings that have survived the cuttings, and pinch the tops of the new branches when they are about 6 cm long. When the secondary buds grow to 6 cm to 8 cm, place the flower pot on its side. The angle of the side tilt is generally controlled at 80 to 140 degrees. When watering and fertilizing, the plant should be placed flat. Depending on the growth of the plant , it can be rotated every 5 to 10 days. At the same time, in order to prevent individual branches from growing too high, after a period of growth, the individual branches can be properly fixed with plastic wires. After a growing period of continuous rotation, the plant can be controlled at 20 cm to 30 cm without branch damage. In late autumn, the flower pot should be placed flat to allow the branches to grow naturally upward and gradually form flower buds. In this way, the total height of the plant can be effectively controlled between 30 cm and 40 cm.        

6. Pruning Poinsettia to Promote Secondary Flowering

Timely pruning: When poinsettia loses its ornamental value, it can be pruned.

The height of the pruning can be determined according to the branching conditions. Usually, 3 buds are left on the middle branches and 3-5 buds are left on the surrounding branches. The branches are cut 0.5 cm away from the lower buds. The cut is horseshoe-shaped and sealed with wax to prevent nutrient loss. After pruning, bamboo strips are used as lining, and brown silk is used to bend the branches around to make them evenly distributed and of the same height. Since the poinsettia has no leaves after pruning, it is better to be bent with a flat head and open shape, so that the flowering bracts are connected evenly, which can make up for the lack of green leaves.

Strengthen management and control watering after pruning.

When the pot soil turns white, apply fully fermented fish and bean cake liquid fertilizer once, and water once after each application of fertilizer. In addition, spray the leaves with 0.2 % potassium dihydrogen phosphate solution twice every 10 days until the flower buds are fixed and stop fertilizing. In order to improve the conversion rate of organic nutrients, it is conducive to the early differentiation of flower buds. The room temperature should be maintained at 15 ℃-23 ℃ during the day and above 10 ℃ at night; and the poinsettia should be provided with sufficient light, not less than 4 hours to 6 hours a day. If the light is insufficient, artificial light can be used to supplement it.

Precautions

1. The pruned poinsettia should be placed in the original place and should not be moved at will, otherwise it will affect the differentiation of flower buds.

2. The temperature of the water and liquid fertilizer used for irrigation must be around 20 ℃. Add hot water to adjust the temperature before watering.

3. Use a bamboo chopstick to make several holes around the pot to help the soil flow through.

4. The indoor temperature is relatively stable, avoiding large temperature fluctuations.

5. As there are no leaves, it is better to place it below the horizon. About 25 days after pruning, buds will sprout between the nodes. One bud per branch is best, but in order to fill the gaps, you can leave a few more in appropriate positions. About 45 to 50 days, the number of red bracts can reach about 21. The width of a single bract is 2.5 cm, the length is 12 cm, and the flower diameter is about 25 cm.

7. Management of Poinsettia before planting

The management of poinsettias before and after they are harvested has a great impact on their quality and shelf life. Proper management can provide high-quality poinsettias with a long shelf life throughout the Christmas season. The shelf life of poinsettias is now much longer than it was 20 years ago. However, if the shelf environment after harvest is not good, the shelf life will still be shortened.

Possible problems of poinsettia after it leaves the field include: drooping and falling of leaves and bracts, falling flowers, yellowing of leaves, browning of bract edges, mechanical damage during transportation, etc. If the production, transportation and sales links are well coordinated, these phenomena can be basically eliminated or the degree of damage can be greatly reduced.

Management practices for poinsettias can affect the shelf life of the poinsettia.

Before the bracts mature, they should be given as high light intensity as possible to help prevent the flower buds from falling off before sales. Too dense placement, high night temperatures or too dry substrate during production will cause immature flower buds to fall off. Excessive levels of soluble salts in the soil in the late growth stage will cause the edges of the bracts to turn brown and the leaves to fall off after transplanting. Flushing with clean water before transplanting will reduce the level of soluble salts in the soil. However, it should be noted that excessive irrigation may also cause permanent damage to the root system, resulting in reduced quality and leaf shedding. In addition, since it is difficult to control the concentration of soluble salts in the soil, it is best to use a slow-release fertilizer with a release period of 90 to 110 days and apply it only once, so that the fertilizer has been almost consumed by the time of transplanting.

Poinsettia must be mature before it can be planted.

Lowering the temperature to 13 ℃ to 15 ℃ in the late planting period can make the bracts color better. There are many poinsettia varieties now, even if some bracts are not fully developed, the bracts are already very red. But if they are taken out of the nursery and moved indoors at this time, the bracts are likely to fade. Therefore, when taking them out of the nursery, the bracts must be fully opened and colored, and the flowers have begun to bloom. Mature poinsettias should be placed in a cool environment as much as possible, but the temperature should not be lower than 10 ℃ to 12 ℃. Because lower temperatures will make the bracts turn blue or white.

Bagging can cause an accumulation of ethylene released by poinsettia plants, which can cause leaves and bracts to droop.

The longer the bagging time, the more serious the drooping of bracts and leaves. Therefore, the packaging must be removed immediately after arrival. Generally speaking, after removing the bag, place the plant in a bright environment with a temperature between 10 ℃ and 23 ℃. The plant will recover after 24 to 48 hours. If the substrate is dry when it arrives, it must be watered thoroughly. If the temperature of the placement environment is not lower than 22 ℃, it should be given 12 hours of light per day with a light intensity of 1100 lux. This can reduce the yellowing and leaf falling phenomenon of leaves. If the temperature is between 18 ℃ and 21 ℃, a light intensity of 550 lux is also acceptable. The environment should be well ventilated, but direct wind should be avoided on the plant. Do not place the plant directly in the sun or place it too close together. Too close will cause insufficient light and increase leaf fall. For varieties with larger bracts, the large bracts will block the leaves below and block the sun. Therefore, it is particularly important to have a certain amount of space for placement. Maintain a certain soil moisture, but be careful not to water too much.

8. Why does the poinsettia drop its leaves?

Teacher Zhu Xuejing from Room 302 , Building 28 , No. 6 Huancheng Road, Zhenjiang City, Jiangsu Province wrote to ask: The green leaves of the poinsettias I grow at home turned yellow and fell off since late October , and only a few small bright red bracts were left. What is the reason for this?

A: There are several reasons why your poinsettia may be shedding petals:

1. The soil in the pot is too dry, and the plant's fibrous roots shrink and are damaged, resulting in a decrease in its ability to absorb water, causing the lower leaves to fall off first.      

2. The soil in the pot is too wet. Due to water accumulation in the pot, the fibrous roots of the plant rot, the plant's ability to absorb water is sharply reduced, and the leaves fall off.      

3. If the leaves become burnt at the edges and then fall off, it is mainly caused by low air humidity. However, your poinsettia does not have burnt edges, so this reason can be ruled out.      

4. The temperature is too low, and the leaves turn yellow and fall off. Poinsettia requires a temperature of at least 13 to 16 degrees Celsius. If the lowest temperature in the morning is lower than this lower limit, or the temperature drops suddenly, it is very easy to cause the leaves of the poinsettia to turn yellow and fall off. In late October this year , the lowest temperature was relatively low for a few days, and this is the biggest reason for your poinsettia's leaf shedding.      

5. Placing the poinsettia plant in a place where cold air blows. In late October , if cold air moves south and the caregiver fails to place it in a place sheltered from wind and cold in time, this is also an important reason.      

6. The light is too weak. Poinsettia likes light very much and can accept full light in spring, summer and autumn. If you move it indoors after late October but fail to create the proper light conditions for it, including increasing the light intensity indoors and appropriately extending the light time, it is inevitable that the leaves will turn yellow and fall off. This is also a possible reason for the leaf shedding of your poinsettia.      

7. If poinsettia is placed indoors, the air will be polluted and oxygen-deficient, and many leaves will fall off overnight.

 When cultivating poinsettia at home, we should pay attention to the following aspects:

First, the temperature. It likes a warm environment. After the bracts turn red, the lower temperature should be maintained at no less than 13 ℃. Otherwise, the leaves will turn yellow and fall off due to the low temperature.

Second, light. In spring, summer and autumn, it can be placed outdoors in a sunny place to make it grow strong. In winter, it should also be given as much light as possible to make it grow strong. Incandescent light can be used as a supplement.

The third is water. In the growing season, the potting soil should be kept sufficiently hydrated, but water should not accumulate. Watering should be done only after the surface of the potting soil is 1 cm to 2 cm dry. Each watering should be done thoroughly. In winter, due to the low room temperature, watering should be reduced to keep the potting soil slightly moist.

Fourth, air humidity. During the flowering period, you should often spray the leaves to increase the relative humidity of the local space. You can also sprinkle water on the ground indoors. If you want to continue to bloom and watch in the second year, you can cut the plant 5 cm to 8 cm from the base after it blooms and bears fruit. When repotting, delete some perennial roots, replace with fresh and fertile culture soil, and then place it in a well-lit place. Strengthen water and fertilizer management to make the plant grow strong and healthy. It can continue to bloom in the second year. Cutting seedlings are generally carried out in spring. After cutting the thick branches, they should be spread out for a period of time. After the milky white juice oozing out of the cut ends is dried, moisturizing sand or soil cuttings can be carried out. The survival rate is higher.

9. Pruning and cutting of poinsettia

After New Year's Day and the Spring Festival, the poinsettia flowers that families grow for the New Year will soon end their flowering period and lose their ornamental value. At this time, you can combine short pruning with hard branch cuttings. The method is:

1. Prune the branches reasonably according to the branching situation of the mother branches.

When pruning poinsettia after flowering, one should focus on continuing to cultivate the mother plant in the future to make it more perfect in shape, with luxuriant flowers and leaves. Therefore, generally, the second to fourth branches around the branches can be kept , and it is best to prune them 0.5 cm above the outermost bud on the top ; while the second to third branches in the middle can be kept , and the direction of the top buds should also be selected. It is best to prune them at the buds that are conducive to filling in the gaps in growth, so as to create convenience for their future upright growth or curved shape.

    2. Cut cuttings and treat wounds.

Since cuttings are prone to new roots at the fullness of the stem nodes, the cut branches should first be cut flat at 0.5 cm below the lowest bud, and the cut should be smooth to remove the empty stem part. Then, from bottom to top, every 3 to 4 buds are cut into a section of cuttings, and finally the tender shoots are removed. While pruning and cutting cuttings, in order to avoid excessive wound flow from the mother plant and both ends of the cuttings, you should pay attention to applying plant ash or sulfur powder on the wound at any time.

    3. Prepare the soil and take cuttings.

Mixing a little plant ash with plain soil as a substrate is very conducive to the survival of cuttings. When cutting, first use a wooden stick as thick as the cutting to make holes on it, and then insert the cuttings directly into the holes, with a spacing of 3 cm to 4 cm. Pay attention to the consistency of the depth of the holes and the cuttings, both of which are based on 1/3 to 1/2 of the cutting length . Do not insert the cuttings too deep or too densely, which will affect the rooting and leaf extension in the future.

    4. Watering and covering with film.

When watering the cuttings, let the water flow slowly along the edge of the pot, and do not sprinkle at a high position. After the water is thoroughly poured, wrap the entire cutting pot with intact plastic film and place it in a warm and sunny place. The room temperature can be maintained above 15 ℃, so that a self-circulating system of high temperature and humidity environment can be maintained. About 20 days, when the hidden buds on the cuttings germinate and grow to 2 cm, the film can be broken appropriately for ventilation, and the ventilation intensity can be gradually increased later. Finally, after the leaves have unfolded and turned green, the film can be completely removed, and normal water and fertilizer management for the seedlings can be carried out. By mid -to-late April , it can be planted in pots in time as appropriate. In this way, the mother plant and the new plant will form a new green because pruning is combined with cutting propagation, so several pots of poinsettia will form a new green.

10. Dwarf Poinsettia Stem Cutting Propagation Method

 Dwarf varieties of poinsettia have changed the shortcomings of traditional old varieties, such as tall stems and branches and difficulty in branching. They save the many measures and troubles of bending branches and controlling height with drugs. However, dwarf varieties of poinsettia also have the difficulty of having short branches and difficulty in taking root without rooting agents.

In order to explore the simplest and most efficient method for dwarf poinsettia propagation, the author conducted a variety of experimental comparisons and found that the method of using dwarf poinsettia branches and leaves from alternate years is the most suitable for family propagation of new plants. No rooting agent is required during propagation, and the survival rate reaches 100 %. On a 30 cm long stem, at least 15 plants can be cultivated during the propagation period from April to June , each with more than 3 branches.

    The specific operation method is as follows:    

【Remove flowers and promote leaf buds 】 

Dwarf poinsettia is different from traditional old varieties. It has a longer flowering period. If it is properly maintained during the flowering period, it can often "bloom" until June of the following year. For the needs of reproduction, the colored bracts on the mother plant should be cut off immediately after the beginning of spring. Apply charcoal ash to the wound, keep the other stems and leaves, and strengthen daily fertilizer and water management to allow it to enter nutritional growth. About 15 days, many new buds will grow in the axils of the stems and branches of the mother plant. Among them, a few buds also have certain small flower buds at the ends. At this time, the small flower buds also need to be removed and coated with charcoal powder to stop the slurry. After about 20 days, especially in the upper half of the mother plant, the length of the newly grown leaf bud stems can reach about 5 cm, and the diameter of the new leaves can also reach about 4 cm.

【Cutting stems and taking cuttings 】

Use a sharp knife to cut the stems with new leaves (the original old leaves can be removed) with 2 to 3 axillary buds on each section (it must be ensured that the cut stems have new stems, buds, and leaves), and then use charcoal powder to stop the upper and lower cuts of the cut stems. Then, spread the stems flat on a clean wooden board in the shade and let the wounds air dry (about two days). For the leaves of the new axillary buds on the lower stems of the mother plant that are less than 4 cm, continue to fertilize and water them, and cut them when the new leaves grow to more than 4 cm. The cutting medium can be fresh rice husk ash, perlite, fine sawdust, coarse yellow sand, etc. But it must be clean and hygienic, and the materials that have never been used. The containers can be seedling boxes, rattan baskets, bamboo baskets, wooden boxes with seams at the bottom, etc.

    【Cutting tips 】 

 First, spread the substrate for cuttings in a container with a thickness of about 10 cm and slightly compact it. Then use a bamboo chopstick to poke a hole about 3 cm deep on the substrate surface, and then gently insert the dwarf poinsettia stem segment into the hole. Make a hole lightly and insert the cutting directly into the hole. Otherwise, the incision will be injured and cause rot, which will affect the survival rate. When cutting, the substrate can be buried in the stem segment of the alternate year, so that the leaf buds are exposed above the substrate surface. Do not damage the leaves. Keep a little distance between the cuttings, and the leaves must not overlap each other to affect the light. Each time you insert a plant, you need to gently compact the substrate around the plant. Finally, water it thoroughly.

    【Post-insertion management 】

The seedling box should be placed in a sunny place indoors. It can be covered with glass for better moisture retention and heat preservation. The rooting time can be shortened by about 4 days, but attention should be paid to the temperature of the seedling box to avoid suffocating the new plants. It is also OK not to cover the glass. Usually keep the substrate a little dry, as long as the new leaves do not droop. After about 1 month, the plant will grow new roots. When the new roots grow 5 cm long, the seedlings can be removed and planted separately.

Key points for planting

① The culture soil should be loose, permeable and rich in nutrients.

② The seedlings must be dug with bamboo strips, and they should not be pulled out hard to avoid damaging the roots. After planting, shade the plants for 5 days, and then normal maintenance and management can be started.

11. Make Poinsettia Bloom on Time

 Poinsettia has now become one of the main potted flowers on the domestic market, and its flowering period is mainly during Christmas, New Year's Day and the Spring Festival.

The blooming time of poinsettia is mostly fixed. If you want the poinsettia to bloom at the scheduled time, you must carry out scientific maintenance based on its characteristics.

1. Substrate: The optimum pH range of poinsettia substrate is 5.5-6.0 . The potting substrate can be made of 2 parts of garden soil, 1 part of leaf mold and 1 part of compost, or 3 parts of peat, 1 part of perlite and a small amount of base fertilizer.

2. Water and fertilizer management: Poinsettia leaves are relatively sensitive. If not managed properly, it is easy to cause the leaves to fall off. Water less in spring and winter to prevent leggy growth. Water once in the morning and evening in summer . Follow the principle of "alternate dry and wet". Water after the pot soil is dry. Prevent the pot soil from being too dry or too wet. Fertilizer should be applied with decomposed sesame paste residue. Apply it to the pot surface in May when the new buds grow, and then loosen the soil; apply it again in early June . Apply liquid fertilizer once a week in June and July , and stop fertilizing when the temperature is high in midsummer. Fertilize once a week after September until before flowering. Phosphorus fertilizer can be applied during flowering to make the flower buds colorful. Do not water too frequently during the flowering period, and control the temperature to extend the flowering period.

3. Environmental control: The optimum temperature for poinsettia growth is 25-29 degrees Celsius during the day and 18-19 degrees Celsius at night. It requires sufficient sunlight. In the shade, the stems are often weak, the leaves are thin, and the yellow leaves are lighter in color. Poinsettia is a typical short-day plant, and it can be made to bloom early through short-day treatment. For example, if you start shading for 4 hours a day in early August , after 45-50 days of treatment, it can bloom on November 1st.

12. Preliminary Study on Poinsettia Cultivation Technology (I)

Poinsettia is native to Mexico and tropical Africa. It is a short-day plant that prefers a warm climate, is not cold-resistant, has strong phototropism, prefers sufficient light, and requires loose and fertile soil with good drainage and ventilation.

It has strict requirements on water and is afraid of both drought and waterlogging.

1. Cultivation medium A good cultivation medium, whether it contains soil or soilless medium, should be light, well-ventilated, have appropriate fertilizer content, and be easy to operate and mix. It should be considered from the following aspects: easy to obtain, good physical properties, less chemical residues, easy to use, light weight, even mixing, high cleanliness, long-term storage, easy potting, high fertilizer content, good fertilizer content, and good adsorption of soluble salts. For soil-based medium formulas, one or more of peat soil, vermiculite, perlite, wood processing byproducts, and foamed refining stone should be added to increase the water retention capacity of the medium and maintain the porosity of the medium to avoid compaction of the medium.

2. Fertilization is very important to achieve the best growth state of poinsettia potted flowers. Poinsettia has a great demand for fertilizer. Fertilization should be started immediately after the cuttings are planted. Sufficient fertilizer should also be added to the planting medium as base fertilizer. Even in the early growth period, insufficient fertilization will affect the quality of the flowers. One month before shipment, the amount of fertilizer should be reduced. On the one hand, it can reduce fertilizer waste, and on the other hand, it can reduce the salt damage that may be caused during the flowering period.

1. Nitrogen fertilizer Nitrogen is one of the main elements required for plant growth, including nitrate nitrogen and ammonium nitrogen. In the soilless medium formula of poinsettia, if there is too much ammonium nitrogen, it is easy to cause yellowing of leaves, and its content should not exceed 33 %. Symptoms of insufficient nitrogen fertilizer are light green or yellowing leaves, slow growth of plants, hardening and lignification of stems, and reduced leaf area.

2. Phosphorus fertilizer deficiency rarely occurs. When the plant lacks phosphorus, the leaf area decreases, the upper leaves turn dark green, and the immature leaves become necrotic.

3. Potassium fertilizer Potassium fertilizer deficiency does not occur often. When the plant lacks potassium, the leaf edges begin to scorch, which usually occurs in the late growth stage.

4. Calcium deficiency often occurs when the pH value of the medium is too low, so 2.5 kg of calcium hydroxide or agricultural lime should be added per cubic meter when preparing the medium . Using calcium nitrate as fertilizer is also an effective way to avoid calcium deficiency and can also provide nitrogen fertilizer.

5. Magnesium deficiency often occurs when producing poinsettia in a greenhouse. The symptoms are yellowing of the leaf edges and yellowing of the veins of the lower leaves. Applying magnesium sulfate to the medium can increase the magnesium content. Adding magnesia lime when preparing the medium can also increase the plant's absorption of magnesium.

6. Fertilization principles The large amount of elements required by poinsettia are usually met by basal fertilizer or regular topdressing. Since poinsettia is growing in soilless media recently, it is also very important to pay attention to adding trace elements such as boron, copper, zinc, magnesium, molybdenum and iron. The specific requirements of poinsettia for nutrients are shown in Table 1. (To be continued)

A Preliminary Study on the Cultivation Technology of Poinsettia (Part 2)

3. Light Intensity and Photoperiod

1. Light intensity Poinsettia likes light, so it is necessary to provide sufficient light (about 60,000 lux) when growing in facilities . Weak light will cause its branches to be slender and weak, slow growth, and premature flower drop, making the potted flowers lose their market value.

2. Photoperiod Poinsettia is a short-day plant. It grows under long-day conditions and differentiates flower buds under short-day conditions. When the night temperature is below 21 °C, the critical photoperiod required for flower bud differentiation of Poinsettia is 12 to 12.5 hours per day. In areas with dark clouds in the morning and evening or lower night temperatures, flower bud differentiation will be slightly earlier; in areas with earlier dawns or higher night temperatures, especially above 21 °C, flower bud differentiation will be later. Flower bud differentiation can usually be completed in 4 to 8 days. The development of poinsettia flowers is very sensitive to photoperiod and temperature. It takes about 5 weeks from the beginning of flower development to full development under short-day conditions. Dark curtains can be used to regulate the flowering period under long-day conditions. Cover the dark curtains for 14 to 15 hours a day, starting at 5 to 6 pm and ending at 8 am the next day.

4. Pinching

Poinsettia is a terminal bud flower differentiation type, but mature branches can form inflorescences. Therefore, in order to produce a plant with many flowers, it is necessary to use pinching to promote the growth of lateral buds and form more branches. Pinching is usually done two weeks after the cuttings are planted, when the new root system begins to grow, which is conducive to the formation of lateral buds. There are strong pinching, moderate pinching, weak pinching, and weak pinching plus removal of young leaves. Strong pinching is to pinch until the leaves are fully expanded, generally about 6 to 7 cm; moderate pinching is to pinch until the two leaves above the fully expanded leaves, generally 3 to 4 cm; weak pinching only removes the heart of the terminal bud, generally within 2 cm. Strong pinching will result in a more open plant shape with neater branches; weak pinching will result in a taller plant shape; weak pinching plus removal of young leaves can increase the number of branches.

5. Height Control

The height of the plant is determined by the selection of growth inhibitors, dosage, application period, variety, temperature and light. Comparative experiments using ccc and pp333 have shown that ccc is prone to causing temporary injury to leaves, and can only effectively control plant height after multiple applications. The most suitable concentration is usually between 1000ppm and 2000ppm ; pp333 has a stronger efficacy, and a lower concentration has a good effect, and the leaves are not easily damaged by the drug. However, when the concentration is too high, the inhibitory effect is too strong, which often has an adverse effect and can shrink the bracts. The most suitable concentration is usually between 5 and 50ppm .

6. Postpartum treatment

Any operation in the production process may affect the quality of poinsettia, such as reduced light intensity, increased night temperature, and excessive drying of the medium. During transportation, poinsettia often causes leaf drop due to high fertilizer concentration, so the fertilizer supply should be stopped or reduced in the last growth stage. Fertilization should not be stopped earlier than two weeks before transportation to avoid yellow leaves. Poinsettia is very sensitive to low temperatures ( below 13 °C), and it is important to maintain proper temperature during handling and storage. If the temperature is too low, the red bracts will turn into cyan or blue, and finally turn silver, and the bracts and flowers will fall off. After the poinsettia plants are transported to the sales location, they should be unpacked immediately, the plants should be removed, and the temperature and humidity of the medium should be checked. If there is insufficient water, water them immediately. Place them in a well-lit room and maintain the temperature between 18 °C ​​and 24 °C. The plants should also be checked for mechanical damage or pests.

13. Dwarfing of Poinsettia

From March to April , after the poinsettia withers, apply liquid fertilizer high in phosphorus and potassium. When the branches are lignified, cut 6 cm to 8 cm strong branches, plug the cut ends with sulfur powder, insert them into clean sand, and place them in a greenhouse at 20 ℃ to 25 ℃. They will take root in about 45 days.

After potting, when the branches grow to 8 cm to 10 cm, pinch the top once. When the new branches grow to 6 cm to 8 cm for the second time, use 10ppm paclobutrazol aqueous solution (add 10 mg of 15 % wettable paclobutrazol powder per liter of water) to water the roots. Since paclobutrazol has good stability in the soil and is not easy to decompose, the plant dwarfs significantly. The internodes become significantly shorter, the leaves grow in layers, and the leaves are bright green, which makes the plant have a better ornamental effect.

14. Rescue of Poinsettia Leaves after Frozen

 Poinsettia branches that have all fallen leaves or have only a few green leaves left should not be watered or sprayed. They should only be placed in front of a sunny and warm window, and the dried leaves that have been scorched should be removed, and the pot soil should be kept at 60 % humidity. Patiently wait for revival and germination. Keep even a small piece of leaves that have not dried up and the top inflorescence that has already bloomed. Do not perform any pruning: if you cut off the top branches that have withered or even dried up, they will continue to dry up. It will be impossible for new buds to sprout from the bottom or the stems of branches without leaf buds.

15. Diseases and prevention of poinsettia (I)

 1. Fungal diseases:

The pathogen is a fungus that infects through wounds, natural openings such as stomata, or surface contact. The most common ones are as follows:                  

1. Root and stem rot caused by Rhizoctonia                              

( 1 ) Symptoms The stems that are in contact with the surface of the medium are most susceptible to infection, especially when the stems are injured or when there is accumulation of fertilizer salts on the surface of the medium. At first, brown but dry patches will appear on the infected parts, which will gradually expand as the fungus grows, even reaching the roots. This fungus is easily carried by the substrate and infected plants, and is easily spread by water. In addition, although they do not have air spores, they can also be spread through infected dust.      

( 2 ) Prevention and control measures: Remove infected plants in time and do not throw away infected branches and leaves at will. Fungicide irrigation has a better effect. Commonly used fungicides include Yili, Ruidumei, Cleary , etc.      

2. Root and stem rot caused by Pythium 

( 1 ) Symptoms The main symptom is root rot. When the roots are infected, brown rot usually appears on the root tip and cortex. The pathogen enters the stem from the bottom up and develops toward the stem tip. The entire stem gradually becomes water-soaked and the color changes from brown to black. Then the cortex of the rotten roots falls off. Infected plants are usually poorly developed, the lower leaves turn yellow and fall off, and in severe cases the entire plant will die. The pathogen is easily spread through water. The disease is prone to occur when the substrate is poorly drained or there is too much water in the substrate. A characteristic of root and stem rot caused by Fusarium is that although the pathogen that causes the diseased plant has invaded the plant in the early stages of cultivation, the rapid development of the roots often conceals the symptoms. When the plant is about to bloom and the root development is slow, the symptoms begin to appear, causing the plant to turn yellow, wilt, and eventually die.      

( 2 ) Prevention and control measures : Fungicide irrigation has a better effect. Commonly used fungicides include: ridomycin, banrot , truban , etc.      

3. Crown and stem rot caused by Phytophthora       

( 1 ) Mycelial morphology: The mycelium of the blight fungus is simple in morphology, with a diameter of 2 to 6 μm. The sporangiophores are irregularly branched or unbranched, terminal, lateral or intercalary, with 1 to 2 obvious papillae that do not fall off.

( 2 ) Symptoms: The pathogen can infect the entire poinsettia plant. Gray to brown or black spots will appear on the stem, and the pith will turn brown. The leaves will initially have brownish-yellow to grayish-brown spots, and eventually the entire leaf will turn brown or black. Sometimes the roots and bracts will rot. As the disease worsens, the entire plant will wilt and die. The pathogen spreads easily in water, and high temperatures and excessive irrigation can easily cause the disease when the plant is mature.

( 3 ) Prevention and control measures: Remove diseased leaves and plants promptly, avoid over-irrigation, and apply fungicides such as rutolide, banrot , and truban for prevention and control.

4. Black root rot caused by thielaviopsis  

( 1 ) Fungal characteristics: The fungus that causes black root rot can survive in the culture medium in the form of sclerotia for a long time. High temperature and slightly acidic medium ( pH below 5.5 ) will inhibit the growth of the fungus.

( 2 ) Symptoms: The roots turn black and rot, sclerotia form in the pith of the stem, and spots form on the back of the lower leaves. The infected plants look lifeless, the leaves turn yellow and fall off, and sometimes the whole plant dies. It is more likely to occur when the temperature is below 16 ℃. With soilless culture medium and fertilizer. Use fungicides such as Yili and banrot for irrigation.

Diseases and prevention of poinsettia (Part 2)

 5. Botrytis cinerea

( 1 ) Fungal characteristics: The spores of Botrytis cinerea float in the air, are everywhere, and like to grow on dead plant tissues or other organisms. It can survive in the range of 0 ℃ to 36 ℃, but is most susceptible to disease at 18 ℃ to 22 ℃. For the germination of spores, a moist plant surface and high relative humidity ( above 90% ) are essential conditions. If the greenhouse is too humid, within a day or two, the pathogen will produce a large number of spores that float in the air and begin to infect plant tissues.

( 2 ) Symptoms: Botrytis cinerea is the most common disease in poinsettia cultivation. It may occur throughout the growing season and any part of the plant may be infected. The infected tissue initially appears as water-soaked brownish-yellow to brownish lesions. Under humid conditions, gray, hairy fungi consisting of mycelium and spores form on the lesions, and black sclerotia appear. Young plants are sometimes infected near the surface of the growing medium. On more mature plants, brownish-yellow annular ulcers appear on the stems and cause the leaves to wilt. When the bracts are infected, the red bracts turn purple.

( 3 ) Prevention and control measures: First, control the water environment and maintain air circulation, especially at night. Using a small fan to enhance horizontal air flow is an effective way to achieve air circulation. Do not place the plants too close together so that air can flow through the crown of the plant. Avoid mechanical damage to the plants. Heat and ventilate at night to reduce humidity and avoid splashing water on leaves and bracts. Keep the temperature above 16 °C as much as possible and remove diseased leaves and dead plants in time. Spray fungicides such as Yili and Botrytis cinerea.

 6. Stem and leaf rot

( 1 ) Fungal characteristics: The spores of stem and leaf rot can be spread through air flow and can survive for a long time in plant residues. It prefers high temperature ( 27-32 °C) and high humidity environments and needs to infect through wounds or weak host tissues.

( 2 ) Symptoms: The disease is most common during the cutting season. When poinsettias are propagated in high humidity, high temperature ( 27-32 °C) and poorly ventilated environments, especially when they are placed too closely together, poinsettia cuttings are very susceptible to the disease. When poinsettia cuttings are infected, their stems, leaves or petioles become very soft and brown and mushy. When the disease infects the stems of poinsettia cuttings, the symptoms are similar to those of stem rot caused by bacterial soft rot, so be careful to distinguish them.

( 3 ) Prevention and control measures: This disease is not common, but it is a potentially devastating disease. Improving the growth environment of the plants or cuttings, such as reducing humidity, will help control the spread of the disease. Pay attention to maintaining a clean environment and be careful to avoid damaging the branches when handling cuttings. At the same time, spraying fungicides such as zyban is necessary.                  

7. Powdery mildew

( 1 ) Fungal characteristics: Powdery mildew spores can easily spread with the movement of plants and through the air. This disease can occur throughout the entire production season of poinsettia, with spring and late autumn being the peak seasons. Powdery mildew can easily spread rapidly in a cold, humid environment with a large temperature difference between day and night.

( 2 ) Symptoms: In the early stages of infection, spots resembling pesticide residues appear on leaves and bracts. Then, powdery mildew spreads rapidly, with typical white mold-like substances appearing on the surface of the plant and infected tissues necrotizing. Powdery mildew symptoms first appear on the underside of the leaves, while green patches often appear on the surface of the leaves.

( 3 ) Prevention and control measures: The occurrence of this disease can be effectively controlled by controlling the greenhouse environment and regularly spraying fungicides. Fungicides such as benefit ,       domain ,       strike , ferraguard , and       zyban can be used for prevention and control.

 8. Poinsettia scab 

( 1 ) Fungal characteristics: Poinsettia scab is mainly spread by water, and spores can be spread by spraying during the breeding period or by splashing water during the growing period. This disease is only effective against poinsettias and several species of the Euphorbiaceae family. This disease is more likely to occur in traditional watering production, especially in unprotected cultivation of poinsettias.

( 2 ) Symptoms: In the early stage of scab disease, angular spots appear around the curled leaves. Then the leaves will develop scab-like lesions, which are light yellow around the leaf spots. In severe cases, scabs with a brown center appear on the branches and petioles. The edges of the scabs are usually white or red. 

( 3 ) Prevention and control measures: Take good care of the early-stage infected plants and spray them with fungicides in time. When spraying, pay attention to spraying the entire plant thoroughly so that the stems can also be sprayed evenly. Systane is the most effective for this disease, and zyban , protect , kocide , etc. also have good prevention and control effects. If the disease is serious, the diseased plants should be packed in plastic bags in time and removed from the greenhouse for disposal.

 9. Other fungal diseases 

 Other fungal diseases occur in poinsettia production, but they are not common, such as oily canker, crown rot, fungal leaf spot, etc.

Diseases and prevention of poinsettia (Part 3)

2. Bacterial diseases

1. Bacterial soft rot 

Symptoms: Bacterial soft rot occurs mainly during the propagation period. Cuttings soften and rot from the base upward within 3 to 5 days of cutting. The disease can be spread by windblown dust, unsterilized tools and the hands of operators. It also spreads easily in water. Therefore, the pathogen can also be found in pond water. Damaged plants, waterlogging in the substrate, high temperatures and factors that weaken the vitality of cuttings can all predispose plants to the pathogen.

Prevention and control measures: The substrate should be thoroughly disinfected to avoid excessive moisture in the cultivation substrate, and the temperature should be kept below 32 °C to create a good growth environment for the plants. No effective fungicide has been found for this disease.

2. Bacterial ulcer disease

Bacterial canker is not very common and usually only occurs in warm, humid conditions. Symptoms include black streaks or spots on green stems, deformed terminal buds and leaves, water-soaked stem cankers with bacterial secretions, brown spots on leaves, and wilting of branches. The bacteria can spread in water and the growing medium, entering the plant through pores or wounds. Control measures: Remove infected plants, avoid showering from the top, keep the temperature low and avoid overheating. Cultivate in a protected area and pay attention to environmental hygiene.

3. Bacterial leaf spot 

Symptoms: This disease affects only the leaves of the poinsettia, causing grey to brown water-soaked spots or patches a few millimeters in diameter. Over time, the spots turn dark brown and the leaves in the infected areas turn yellow. In severe cases, the leaves may fall off.

4. Bacterial stem rot

Symptoms: Mainly stem rot, usually occurs in plants placed under relatively high temperatures. At low temperatures, it generally only manifests as growth stunting and vascular discoloration. The latter two bacterial diseases often occur under open-air cultivation conditions.

The prevention and control measures are: disinfect the substrate, remove diseased leaves and plants in time, and spray fungicides regularly.           

 3. Viral diseases  

There are two main viral diseases of poinsettia, one is Poinsettia Mosaic Virus and the other is Poinsettia Recessive Virus. Poinsettia Mosaic Virus causes the plant's leaves to become mottled, but it may not show any symptoms at all. Cuttings taken from infected plants have been found to root at the same rate as healthy plants. Another Poinsettia Recessive Virus, discovered in 1980 , also does not show any symptoms in poinsettia plants. In general, viruses do not cause serious damage to poinsettias. Neither greenhouse whitefly nor potato whitefly spreads Poinsettia Virus.           

 4. Nematodes

Although called " nematodes " , they are neither insects nor fungi or bacteria, but are an independent category. Many nematodes are saprophytic and live on dead or decaying organic matter.

Poinsettias are very susceptible to nematodes. It is generally believed that nematodes themselves do not cause much damage to the plant, but they can cause other pathogens to invade and form secondary infections, which can cause serious damage to the plant. Although nematodes are not airborne, they can be easily spread by contaminated substrates, garbage, water, etc. If the disease is well controlled, the damage caused by nematodes is not serious. However, in general, other diseases can be found in the land where nematodes are found.

Nematodes are more sensitive to fumigation and air disinfection than most fungi and bacteria, so routine disinfection can kill nematodes.

16. Elements of Poinsettia Cultivation ( I )

1. Light

Light intensity, light quality and photoperiod are three factors that must be considered in poinsettia production.      

1. Light intensity 

 Poinsettia is native to Mexico and prefers warm climates and sufficient light. When the temperature is high, the light intensity required during the vegetative growth season is 400,000 to 60,000 lux . The stronger the light, the higher the photosynthetic rate. Therefore, as long as the temperature is within the appropriate range, sufficient light should be given as much as possible. Under low light conditions, the branches of the plant become weaker, the growth rate slows down, and the thin branches cannot support the weight of the bracts and flowers. At the same time, low light intensity can easily cause uneven development of flowers and delay flowering, thus affecting the quality of potted flowers. In addition, after the bracts mature, if they are placed and sold under very low light conditions, they will fall prematurely.

Although poinsettia likes sunlight, it needs to be shaded moderately in the hot summer. It is recommended to use 70% shading nets to reduce light intensity and thus reduce heat stress. Cultivators in the south should pay special attention to increasing shading when the greenhouse temperature exceeds 32 ℃. In the south, it is advisable to remove the shading nets in early October to avoid the phenomenon of delayed flowering due to excessively high temperatures during the flower bud differentiation period. In the north, it is advisable to remove the shading nets in early September to ensure sufficient light. In the late stage of cultivation, the light intensity in the north drops sharply, especially on cloudy days. In order to reach the light compensation point, supplementary light is necessary, and it is more appropriate to provide light of not less than 3000 lux .

In the early stage of potting, the root system has not yet grown well, and the plant is easily damaged by water loss. It is necessary to increase shading, especially when the temperature is high. The shading can be gradually reduced as the root system grows. In addition , about 15 days before the nursery, it is advisable to provide moderate shading to adapt to the sales and display environment and extend the display life.     

 2. Light quality

Light quality is important for flowering and stem elongation of poinsettia. Red light is more effective than daylight in preventing flower bud differentiation. Therefore, when adding light, incandescent lamps are generally used instead of fluorescent lamps to maintain the vegetative growth of the mother plant. From the perspective of stem elongation, when the ratio of far-red light to red light is large, it is beneficial to the elongation of plant stems and detrimental to the differentiation of lateral buds. Therefore, when the plants are placed too densely, the red light can reach the stems due to the mutual shading between the leaves, increasing the ratio and causing inter-branch elongation. Extra growth can be achieved by increasing the spacing between plants. Sufficient growth space is important for the good development of branches and the formation of tight, healthy branches.     

 3. Photoperiod and flowering characteristics of poinsettia

The photoperiod refers to the number of hours of light or dark periods per day, which determines whether the plant maintains a vegetative growth state or enters a reproductive growth state. Poinsettia is a typical short-day plant, that is, it grows vegetatively under conditions of long days and short nights, and enters reproductive growth under conditions of short days and long nights. Under normal natural conditions, the critical point is 12 hours and 20 minutes in day length. When the day length is shorter than this critical point, poinsettia switches to reproductive growth and begins flower bud differentiation. Therefore, the day with a day length of 12 hours and 20 minutes is generally called the critical day. 5 to 7 days after the critical day deficit , flower primordia can be seen under a microscope. Due to the vast territory, the dates of reaching the spider primordial day vary greatly from place to place, but the determination of the time of flower bud differentiation is of great significance to the formulation of production plans. Before planting poinsettia, be sure to find out the local critical date.

In order for poinsettia to enter reproductive growth, the following two conditions must be met:      

1. Continuous short-day sunshine

Poinsettia requires short-day conditions from the beginning of flower bud differentiation to full development, that is, under suitable temperature conditions, the length of the day must be less than 12 hours and 20 minutes. Under natural light conditions, the time required from the critical day to the growth of a saleable flower is called the short-day induction time. The short-day induction time of different varieties varies to a certain extent, generally around 8 to 10 weeks. However, due to the fact that merchants have been promoting Christmas earlier and earlier in recent years, the selection of early-maturing varieties has become the mainstream of poinsettia breeding, and now there are varieties with an induction time of 6.5 weeks to 7 weeks.

The selling date can be calculated based on the short-day induction time. That is, the critical point date, short-day induction time = selling date. For example, assuming that the critical day of a region is around September 25 , then for varieties like Germany's " Rich Red " with an induction time of 6.6 weeks to 7 weeks, the selling date is November 10 to 13 , and for varieties with an induction time of 10 weeks, the selling date is around December 4. Due to the importance of the short-day induction time , the induction time of the variety is generally given in the variety introduction. Poinsettia growers can choose varieties according to their needs and production and sales arrangements.

2. Keep the night temperature below 24 ℃

Night temperature has a great influence on the differentiation of poinsettia flower buds. Night temperatures exceeding 24 °C will completely inhibit the differentiation of flower buds, and the plant will continue to grow even if the day length is less than 12 hours and 20 minutes. In hotter areas, the starting time of the critical day should not only consider the critical day length, but also the night temperature. For example, in Guangzhou, the critical point of flower bud differentiation is around September 23 , but the night temperature at this time is still higher than 24 °C. Then, the starting time of the critical day should be postponed to around October 1 to 5. However, when the northern region reaches the critical day, the night temperature is generally not below 24 °C, so no special consideration is required.

Elements of Poinsettia Cultivation ( Part 2 )

2. Temperature, water and flowering period control

1. Control of the flowering period of poinsettia 

Under natural light conditions, poinsettia blooms in November and December . This is why poinsettia is also called " Christmas flower " and " Christmas red " . If you want to control poinsettia to bloom and be sold during the National Day or Spring Festival, you must carry out special treatment.      

( 1 ) Adjustment of flowering period for National Day 

To make poinsettia bloom early, it is necessary to create artificial short days under natural conditions of long days, that is, cover the flowers with a black curtain. To ensure the short day effect, the black curtain should be covered for about 14 to 15 hours a day, that is, from about 5 to 6 pm every day until about 8 am the next day . The black curtain treatment will increase the night temperature, so special attention should be paid to the night temperature not exceeding 23 ℃, otherwise all efforts will be in vain.

In areas where the night temperature is higher than 21 ℃, it is best to open the black curtain after the night is completely dark to help dissipate heat, and then cover the black curtain again before sunrise. As long as the night length is determined to be 13 hours, it will not affect the differentiation and development of flower buds. In the south, it is difficult to control the night temperature below 23 ℃ from July to September . Therefore, it is generally not suitable to produce poinsettias that bloom on National Day in the south. In Central China, East China, and Southwest China, if you want to produce poinsettias that bloom on National Day, you also need to open curtains to cool down at night, and the production cost will increase accordingly. Northwest, North China, and Northeast China are very suitable for producing poinsettias that bloom on National Day. It should be noted that when the night temperature drops sharply to below 13 ℃, it is best to heat it.

( 2 ) Adjustment of flowering period during the Spring Festival:

In order to delay the flowering and sale of poinsettias until the Spring Festival, it is necessary to extend the day length by adding light at night so that the plants can maintain vegetative growth. Generally, as long as there is a light intensity of about 100 lux around the height of the plant , the differentiation and development of flower buds can be prevented. In the middle of the long night, such as from 10 pm to 2 am the next day , adding light has a good effect. The date of closing the lights can be obtained by reversing the previous formula, that is, the date of sale - sensing time = the date of closing the lights, but it should be noted that after adding light, the sensing time of some varieties will be different from that under natural light conditions. In addition, low temperature will slow down the development and color change of bracts, and the speed of bract development and color change will vary between different varieties. This should also be taken into account when calculating the date of sale. The cost of heating in winter is very high when producing poinsettias that bloom during the Spring Festival in the north, so it is generally not recommended to produce them in the north. If you want to produce them, the night temperature should be kept above 13 ℃. In addition, since the total solar radiation in the north is small in winter, it is best to supplement light during the day on cloudy days. Through black curtain treatment or light treatment, as long as the night temperature does not exceed 23 ℃, you can grow poinsettias all year round.

2. Temperature  

Temperature is the main factor affecting the growth and development rate of poinsettia.

( 1 ) Effect of temperature on growth rate:

 Poinsettia generally cannot withstand sub-zero temperatures. In the case of strong winds, 5 °C can cause frost damage to poinsettia. The optimum night temperature for poinsettia is 16 °C -21 °C, and the optimum day temperature is 21 °C -29 °C. In general, the optimum growth temperature is generally between 16 °C -27 °C. When the temperature is below 16 °C, poinsettia grows and develops very slowly; if it is below 13 °C, its growth will stagnate. On the other hand, although poinsettia can tolerate temperatures above 29 °C, temperatures above 29 °C are not good for the growth of the plant. When the poinsettia plant is exposed to high temperatures above 35 °C for a long time, it will gradually die due to the stress of the high temperature.

The rate of vegetative growth and the degree of flower bud differentiation of poinsettia can be estimated by the rate of leaf growth and expansion. Before the flower buds can be distinguished by the naked eye, the rate of leaf vegetative growth can be used as a basis for judgment. The basic growth temperature for poinsettia leaf expansion is about 5 to 9 ℃, and leaf growth stops below this temperature. As the temperature rises, the leaf growth rate accelerates, and one leaf develops about every 4 to 5 days. When the temperature reaches 25 ℃, the leaf growth rate reaches the maximum. After the temperature is above 25 ℃, the leaf growth rate gradually slows down.

If the growth rate of the plant can be accurately controlled so that the plant develops a certain number of leaves before the flower buds differentiate, the quality of the poinsettia potted flowers produced each year can be kept stable. Because the inflorescence of poinsettia is differentiated at the end of the branch, it is greatly affected by the number of leaves on the branch. In addition, the number of leaves on the branch will also affect the size and shape of the plant's appearance.      

( 2 ) Effect of temperature on internode elongation:

The length of internodes is greatly affected by the temperature difference between day and night. The length of internodes and plant height increase with the increase of the temperature difference between day and night. For example, plants grown at 24 ℃ day temperature and 18 ℃ night temperature have longer internodes and higher height than plants grown at 21 ℃ day temperature and night temperature, even though the average daily temperature is the same. Therefore, the change of the temperature difference between day and night can be used to adjust the growth rate of internodes and thus control the height of plants. This effect is greatest between 3 weeks after pinching and when the pollen sacs and stamens are visible. 

( 3 ) Effects of temperature on flower bud differentiation and development:

As mentioned earlier, even under short-day conditions, night temperatures above 23 °C will hinder the differentiation of flower buds. This feature can be used to produce products with delayed flowering. For plants with delayed topping or plants that are lagging behind in growth, the night temperature is raised to 25 °C to accelerate plant growth and delay the differentiation of flower buds, allowing the plant to complete vegetative growth. When the plant height is adjusted to an acceptable range, the temperature is lowered to allow the flower buds to differentiate, thereby producing mature flowers of relatively consistent quality. Average temperature has a great impact on the speed of flower bud development in poinsettia. When the temperature is between 16 °C and 21 °C, the higher the temperature, the faster the flower bud development. However, when the temperature exceeds 21 °C, the speed of flower bud development will slow down. In addition, the average temperature will affect the speed of bract development and the final size of the bracts. When the temperature is maintained at an average of 20 °C, the differentiation and development of bracts are ideal. In the later stage of growth, lowering the temperature to 15 ℃ -17 ℃ will help the bracts change color, slow down the maturation of the inflorescence, reduce premature flower drop, and help maintain the quality of the finished product during transportation.

Elements of Poinsettia Cultivation ( Part 3 )

  3. Water quality  

 High - quality water is an important factor in the successful cultivation of poinsettia . the factors affecting water quality mainly include ec value , ph value , sar value , carbonate , sodium ion , calcium ion and other factors . in addition , excessive content of boron , fluorine , sulfur , iron or other soluble salts will hinder the absorption and growth of some nutrients of poinsettia , or cause excessive absorption of certain elements and cause toxicity . the main standards for water quality assessment are shown in table 1

In the north, due to the increasingly serious desertification problem in recent years, groundwater is decreasing, the dissolved salt content is increasing, and the pH value is rising, which seriously affects the water quality. The pH value of water sources in some areas even reaches 9. The alkalinization problem has seriously affected the development of the flower industry. When we simply use sulfuric acid or phosphoric acid to neutralize it, the plants will be poisoned by the excessive amount of certain elements. The water quality in the south should pay attention to the problem of excessive iron and manganese content. In the water quality management center, the interaction of various factors must be fully considered to effectively improve the water quality.

The following are frequently encountered water quality problems and solutions:

 chart      

1. EC value ( mmhos ) Total amount of dissolved salt ( ppm ) Sodium content in dissolved salt ( ppm       )     SAR value     pH value Chlorine (ppm)     Sodium (ppm) Boron (ppm) Iron (ppm)              

 0.25-0.75175-52520-403-56.5-6.8

    108-144    50-69    0.3-0.5    1-30.75-2.0    525-1400    

40-605-106.8-7.0144-21669-1380.5-1.03-52.0-3.01400-2100

    60-80    10-15    7.0-8.0    216-360    138-207    1.0-2.0   

 5-10>3.0>2100>80>15>8.0>360>207>      3    >10

( 1 ) Iron and manganese

 There are two forms in water: a reduced soluble form and an oxidized, less soluble form. Due to the lack of oxygen, groundwater has a high proportion of iron and manganese in reduced soluble forms . However, when the water is sucked up and exposed to the air, the iron and manganese are oxidized into less soluble forms. Water with high iron and manganese content will form black, brown or rusty colors on the leaves. Solution: Pump groundwater into the pool in a spray state to allow the iron and manganese to oxidize quickly or become insoluble, and then slowly settle to the bottom of the pool, and pump the water above for use. Manganese oxidizes much slower than iron, so it sinks to the bottom of the pool much more slowly. Chemical coagulants can be used to precipitate manganese from the water.

( 2 ) Calcium and magnesium 

Hard water is caused by excessive calcium and magnesium in the water . Plants have a high tolerance to calcium and magnesium , so hard water rarely causes direct damage to plants. However, using hard water to remove algae will cause serious salt accumulation on the leaves. Using a water softener can remove calcium and magnesium from the water. Most softeners use sodium to dissolve calcium and magnesium. High sodium softening factors will cause serious damage to plants and should not be used. Potassium can be used to replace calcium and magnesium softeners and as a source of fertilizer.

( 3 ) Carbonates and bicarbonates 

Excessive carbonate and bicarbonate levels can produce many side effects, such as severe salt deposition during sprinkler irrigation, precipitation of nutrients, especially trace elements, during liquid fertilizer application, and increased pH values ​​over time, which can easily lead to iron and manganese deficiencies. Acidification can remove these two salts from water.

( 4 ) Fluorine  

 Fluoride pollution comes from fertilizers (especially superphosphates), growing media (especially perlite) and irrigation water. Most irrigation water contains 1mg/l or less of fluoride, which is generally not a problem, but too much can harm plants. It is usually adsorbed with activated alumina or activated carbon.

( 5 ) Boron  

 Boron is present in many irrigation waters. Small amounts ( 0.3 to 1.0 mg /L) are ideal. Boron usually occurs in the form of borates, which can be removed by anion replacement, but this is expensive.

Elements of Poinsettia Cultivation ( IV )

 3. Fertilizer

1. Basic principles of fertilization

In the past, soil mixed substrates had strong buffering capacity and could provide sufficient trace elements for the growth of poinsettia. Modern cultivation using soilless substrates often lacks trace elements and has poor buffering capacity. It is necessary to add some necessary elements during irrigation. Poinsettia often suffers from elemental deficiencies, especially the lack of calcium, magnesium, molybdenum, manganese, zinc and other elements. Therefore, complete formula fertilizers must be applied to produce high-quality poinsettias. At present, there are two major types of complete formula fertilizers for poinsettia. One is wrapped slow-release granular fertilizers. This type of fertilizer uses a special coating to wrap the fertilizer and slowly release the fertilizer in the substrate. Its advantage is that it is easy to use. The disadvantage is that the release rate of this type of fertilizer depends on the land temperature or the substrate humidity, which is difficult to synchronize with the needs of the plant. There may be excessive local salt dissolution in the substrate, causing root damage. The other type is liquid fertilizer. The advantage of liquid fertilizer is that it can keep the roots of the plant at a better fertilizer concentration and can adjust nutrients according to the local water quality and plant growth conditions. The disadvantage is that each application is more labor-intensive.

The concentration of poinsettia fertilizer is based on nitrogen. If fertilizer is added to each irrigation water, the recommended nitrogen concentration is 150-200ppm . If fertilizer is applied once a week, the recommended concentration is 250-300ppm . The ratio of nitrogen, phosphorus and potassium can be 20:10:20 . Most complete fertilizers provide enough nitrogen, phosphorus, potassium and all necessary elements, such as iron, magnesium, boron, molybdenum, manganese, zinc, sulfur, etc. Complete fertilizers are best used in combination with local water quality. The water quality in each region is different, so the fertilizer ratio in each region is also different. Because if the content of a certain element in the water quality is too high, if the ratio is not changed, it will cause poisoning or affect the absorption of other elements.

Generally, poinsettia has different fertilizer requirements at different growth stages. The first month of cultivation is the key period of the entire growth season of poinsettia, and the concentration of nitrogen and potassium can be appropriately increased at this time. When the flower buds of poinsettia differentiate and the bracts turn red, the ratio of nitrogen, phosphorus and potassium should be adjusted to normal. During the flowering period, the fertilizer ratio should be adjusted to increase the phosphorus and potassium content and appropriately reduce the nitrogen content.

2. Element deficiency and element excess

( 1 ) Nitrogen 

Nitrogen is a basic component of protein and chlorophyll. Nitrogen deficiency begins with yellowing of old leaves. At first, the leaves turn light yellow-green, then yellow, and then seriously fall off from the base upward. Growth is slowed, leaves become significantly smaller, and internodes become shorter. The poor growth caused by severe nitrogen deficiency in the early stage cannot be fully compensated in the later stage. Late nitrogen deficiency will cause bracts to become smaller. Excessive ammonium nitrogen will cause poor root growth, yellowing and falling of leaves, and growth stagnation.

( 2 ) Phosphorus 

Phosphorus-deficient plants will grow slowly, the upper leaves will turn dark green, the lower leaves will turn yellow from the edges, and in severe cases, they will die. The tissue between the veins will wrinkle and the texture will become rough. The height, dry weight, number of leaves and leaf size of the plant will all be greatly reduced. Excessive phosphorus will lead to the deficiency of trace elements.

( 3 ) Potassium  

Potassium's basic function is to open and close stomata, so it has an indirect effect on the rate of photosynthesis. Potassium deficiency can cause the lower leaves to turn yellow, the edges to dry and burn, and even the leaves to die. However, dead leaves can still be attached to the plant for a period of time. All leaves except the most tender ones will be affected. Excess potassium can cause magnesium deficiency or salt poisoning.

( 4 ) Calcium 

Calcium deficiency can cause incomplete growth of the growing point and death of the tips and edges of new leaves. Calcium deficiency can also cause sodium to accumulate to toxic levels. Excessive calcium can cause nutritional imbalance and iron or other trace element deficiencies, leading to leaf chlorosis.      

( 5 ) Magnesium

Magnesium deficiency will seriously inhibit the growth of the plant. The lower leaves will turn green between the veins, and the leaf surface will wrinkle. Later, necrotic spots will appear on the leaf margins and between the veins, eventually leading to the death of the entire leaf.      

( 6 ) Iron

Iron deficiency can cause young leaves to turn yellow, but the veins remain green. This is different from manganese deficiency, which can cause young leaves to turn yellow. Extreme iron deficiency can cause new leaves to turn white. Excess iron is generally not harmful.

( 7 ) Manganese 

Manganese deficiency can cause the top leaves to lose green color in a net-like pattern and become rough on the surface, while excess can cause old leaves to turn yellow, die or dry up at the edges.

( 8 ) Zinc  deficiency first manifests itself on new leaves, which become longer and narrower, followed by the appearance of dry, necrotic areas on the leaves. Plant growth is only slightly inhibited. Excessive intake can cause partial plant death.      

( 9 ) Boron 

Boron is related to cell division and elongation. Boron deficiency will cause the growth point to stop growing and the stems and leaves to develop abnormally. Excessive boron will cause the edges of the leaves to turn yellow or dry up, starting with the old leaves.

( 10 ) Copper 

Copper does not move in the plant body, so copper deficiency first manifests itself in young organs. Young leaves and growth points become twisted, grow slowly, and even cause growth point necrosis. Excessive copper can cause root death.

( 11 ) Molybdenum 

Molybdenum deficiency can cause newly mature leaves to turn yellow, dry up at the edges, and curl upwards. There are very few reports of damage caused by high levels of molybdenum.

Elements of Poinsettia Cultivation (V)

 Matrix

Choosing the appropriate growing medium is very important for the cultivation of poinsettia. The most important point about the growth medium of poinsettia is that it must be clean and provide suitable physical properties for the growth environment of the root zone.

Today, most growing media are peat-based mixed media, usually with one or more of perlite, vermiculite, ceramsite, sawdust, bark or sand added to the mix. These mixed media are not only suitable for poinsettia cultivation, but also for most potted plants. The combination of media can be varied, but the basic requirements in the preparation of the media are consistent, including: good drainage, and at the same time, good humidity can be maintained between irrigations to ensure the needs of the plants. On the one hand, it contains relatively low soluble salts, and on the other hand, it has sufficient ion exchange capacity to retain and supply the necessary elements for plant growth.

1. The substrate can be produced in a standardized manner so that the properties of each batch of substrate produced are uniform. The standardized and uniform substrate can implement standardized fertilization and irrigation plans in cultivation.

2. Normally absent soil pests, pathogens, nematodes and weed seeds.

3. After pasteurization, the biological and chemical properties of the matrix remain stable and no amides are released when heated or chemically treated.

Since peat soil contains relatively few pathogens, grass seeds, and toxic substances, and can provide good physical properties, including good porosity and excellent water holding capacity, as well as good ion exchange and buffering capacity, most commercial substrates use mixed substrates based on peat. A good peat mixed substrate contains at least 50% peat and perlite, vermiculite, fermented bark, etc. mixed in a certain proportion.

If growers mix their own soil-containing cultivation substrates, they should pay attention to the cleaning and disinfection of the substrates. Steam sterilization is the best way to clean and disinfect the substrate. The substrate should be heated to 160°F (71°C) with steam for 30 minutes. Check the thermometer frequently to determine whether the temperature required for sterilization has been reached, and test the temperature of each point at multiple locations to see if the required temperature has been reached. Chemical agents such as formaldehyde or methyl bromide can also be used to sterilize the substrate, but appropriate equipment is required and it should be done outdoors and in warm weather.

The key factor affecting the effectiveness of trace elements is the pH value of the substrate. The most suitable pH value for poinsettia growth is 5.5-6.5. Too high a pH value will reduce the effectiveness of iron, manganese, zinc, etc., and will also reduce the effectiveness of calcium, magnesium, and molybdenum. When the pH value is not suitable, the pH value can be adjusted to the appropriate range by adding sulfur soil or iron sulfate to lower the pH value, or adding lime to increase the pH value.

Most producers usually like to prepare the substrate by themselves, thinking that it is not expensive. On the surface, it seems that the prepared substrate is more expensive, but professionally prepared substrates have strict requirements in terms of particle porosity, air permeability and pH value, and the substrate has been strictly sterilized. It is worthwhile to use a small amount of money to ensure the smooth progress of future production, compared to investing in seedlings, manpower and fertilizers, and then the quality decline or even production failure due to substrate problems. Therefore, when choosing a substrate, price should not be the main choice and purchase basis.

5. Ventilation and humidity

1. The role of greenhouse ventilation

( 1 ) Air flow can improve the temperature of the growth environment and help maintain the optimal growth temperature.

( 2 ) Air flow can replenish the carbon dioxide consumed by photosynthesis in the growth environment in a timely manner, keeping the carbon dioxide content stable, thereby improving photosynthetic efficiency. In addition, under strong light, without raising the temperature, just increasing air flow will cause plants to perform more photosynthesis and absorb more water, which means that more nutrients are absorbed at the same time, making the plants grow stronger.

( 3 ) Air flow can effectively reduce the relative humidity around the plant. Appropriate humidity is very important for poinsettia, and regulating relative humidity is the key to the problem. Gray mold, powdery mildew, black spot, etc. are all related to humidity, so if the relative humidity is well controlled, the disease can be effectively suppressed.

In summer, greenhouses generally have the problem of over-temperature. It is impossible to maintain the required temperature by ventilation facilities alone. Water curtain cooling and high-pressure spray are currently the best cooling methods, but they have the disadvantage of high relative humidity. If used in combination with ventilation facilities, the effect will be better. Poinsettia grows best at a relative humidity of 70% to 75%. When the temperature drops at dusk, the relative humidity will rise. At this time, the spray and water curtain fan should be stopped to allow the water droplets on the surface of the leaves to evaporate and prevent the leaves from being wet for 8 hours in a row.

In winter, once the sun sets, the temperature in the greenhouse drops sharply, the relative humidity increases rapidly, reaches the dew point, and dew begins to appear on the leaves. Such high humidity conditions are very suitable for the reproduction of pathogen spores. The side windows of the greenhouse should be opened for ventilation before the temperature drops to the dew point. If the greenhouse has heating conditions, it is best to heat it before the temperature drops to the dew point to reduce the relative humidity.

2. Humidity requirements of poinsettia at different growth stages

( 1 ) From transplanting to topping: At this time, the humidity changes greatly because the seedlings have just been transferred from the cutting environment to the potted environment. It is necessary to increase the humidity to allow the seedlings to adapt to the new environment so that they can grow normally. During the hottest time of the day, spray continuously to maintain a relative humidity of 80% to 90%.

( 2 ) From topping to flower bud formation, the relative humidity should be maintained at 70% to 75% to facilitate the germination and normal growth of poinsettia.

( 3 ) From the stage of flower bud formation to flowering, the relative humidity should be gradually reduced to no more than 70% to reduce the occurrence of gray mold. In winter, the relative humidity of heated greenhouses in the north is often lower than 50% during the day. It is necessary to spray the ground around 10 am to increase the relative humidity, and open the windows for ventilation around 4 pm to reduce the relative humidity.

Elements of Poinsettia Cultivation (VI)

6. Height Control

Height control of poinsettia has always been a difficult point in poinsettia cultivation. To produce perfect poinsettia that meets international standards (crown : height  >1:1.3 ), height control is necessary. In addition to the influence of environmental factors such as variety, temperature, relative humidity and light intensity, the height of poinsettia is also significantly affected by irrigation methods, cultivation space and planting schedule. In the production process , we should first try to control the height by controlling the environment and using different cultivation methods to control the height of poinsettia, such as reserving enough space, providing enough light intensity and reducing the temperature difference between day and night. When it is time to use growth regulators, growers should fully consider the following principles :      

1. Avoid using growth regulators if possible, and use them as little as possible. Improper use of growth regulators may cause some adverse side effects, including reduction in bract size, wrinkled leaves, yellow spots on leaves, and burnt edges. Therefore, be especially cautious when using them and try before use.      

2. Different varieties have different requirements for growth regulators. Although excellent poinsettia varieties are much shorter than traditional poinsettia varieties, in conventional cultivation, growth regulators are often applied to achieve better results. Different varieties have different requirements for growth regulators. For example, the dosage of " Tango " and " Pretty Girl " is slightly higher; while " Samba " does not need or only needs a small amount of growth regulators.      

3. Depends on the growth environment factors. Generally speaking, when the temperature is high, the humidity is high, the planting is dense, and the light is low, a higher concentration of growth regulator is needed. However, under high temperature conditions, high concentrations are likely to have side effects.

4. Depending on the different growth stages, it is generally not necessary to apply growth regulators from the transplanting of seedlings to topping. The best time to apply in the vegetative growth stage is two weeks after topping, which is relatively safe. It is generally not recommended to use it in the flower bud differentiation stage. If you want to apply growth regulators, try to apply them before the flower bud differentiation period. Late application will delay flowering and reduce the number of leaves.

 5. Depends on growth conditions

Strong plants can tolerate higher concentrations of growth regulators. Weak plants should be carefully selected for both the drug and the concentration.

6. Try to choose growth regulators with stable sources

Because sometimes the efficacy of the same agent produced by different manufacturers is not exactly the same, producers choose growth regulators with a stable source to better control the amount of the agent used. In poinsettia production, dwarfing agents generally use chlormequat, b9 (Bijiu), paclobutrazol and chloranil.

In poinsettia production, other growth regulators such as gibberellins and adenine are also used, but they are not yet fully mature and have not been widely promoted in production.

17. Packaging and Transportation of Poinsettia

Modern poinsettia packaging includes the product name and trademark, logo, shipping box and special bag. The combination of product name, trademark and logo forms a brand, which is the manufacturer's logo to sellers and direct users, and is synonymous with product quality. At the same time, good packaging can expand the sales range, otherwise it can only be sold locally.

1. Poinsettia Packaging 

The packaging of poinsettia includes shipping boxes, special sleeves and pallets. Product standardization is the premise of brand packaging. Because the specifications of the packaging boxes are unchanged, the height and width must be unified to avoid waste and increase transportation costs.

1. Packing box specifications 

The cardboard should be hard enough to resist bumps and compression. The net height of the packaging box should be the height of the plant and the pot plus 4 to 6 cm. The length and width of the inner box should be multiples of the pot diameter, but the size and weight should be convenient for one person to carry. Since the crown of poinsettia is large and the bracts are easily damaged, it is recommended to pack with a side opening.

2. Poinsettia special bagging 

The material for the bag should be soft wrapping paper or plastic. The diameter should be 3 to 4 cm larger than the pot diameter, and the length should be 3 to 5 cm higher than the leaves and bracts of the plant .

 3. Design method of pallet

The function of the card board is to fix the flower pot. There are feet on both sides of the card board, and the height of the feet is preferably 3 to 4 cm away from the pot mouth. The diameter of each pot hole in the card board should be about 0.5 cm smaller than the diameter of the flower pot at the height of the card board .

2. Mode of transportation 

Domestic flower transportation usually includes air, road, and rail transportation. The air freight is relatively high, but the product quality is basically not affected due to the short transportation time. However, the quality of domestic air transportation services is not high at present. Potted flowers are fresh products. Workers habitually load and unload potted flowers as fresh cut flowers, without paying attention to the signs that they cannot be inverted, which greatly increases the chances of potted flowers being damaged. The claim procedures are relatively cumbersome, all of which greatly weaken the competitiveness of air transportation. Road transportation is currently the most popular way to transport potted flowers. The freight is only 1/3 to 1/4 of air transportation , and the damage caused by loading and unloading can be minimized. However, the transportation time is generally longer, and the long-term high or low temperature conditions during transportation can easily cause serious transportation damage to poinsettias. Therefore, insulated vehicles or heated vehicles must be used for transportation in winter. The price of an insulated vehicle is 1/3 higher than that of a general semi-enclosed vehicle , and the price of a heated vehicle is more than half higher than that of a semi-enclosed vehicle. In areas south of the Yangtze River, insulated vehicles are generally sufficient, while heated vehicles should be used as much as possible in areas north of the Yangtze River. The price of rail transport is about 1/4 to 1/5 of that of air transport . The freight is cheap but the cargo volume is relatively large and the loading and unloading damage is also large. Reducing the pot diameter, controlling the height and using light substrates are the most effective ways to reduce transportation weight and volume, thereby saving transportation costs.                        

3. Transportation Requirements 

1. Temperature 

The most suitable temperature is between 12 ℃ and 18 ℃. If the temperature exceeds 18 ℃, the leaf bracts will droop more. If the plant is transported at 2 ℃ to 10 ℃ for a long time, cold damage will occur, including leaf bracts wilting, leaf falling, and bluish color of bracts.

2. Moisture 

Generally, the crops should be watered thoroughly one day before loading. Bags and boxes should be put into boxes when the soil is moderately moist.

3. Fertilizer

Do not apply fertilizer before transportation to prevent root burns and leaf bract damage.

4. Loading requirements

The gap between the packaging box and the car compartment should be as small as possible. Large gaps should be filled with foam or other materials as much as possible.

5. Arrival processing

Upon arrival, the packaging must be removed immediately and the plant placed in a bright environment between 18 °C ​​and 23 °C. The longer the poinsettia is in the bag, the more time it will take to recover. If it is too long, it will not recover. Therefore, the transportation time should be as short as possible, preferably no more than 3 days.

18. Management of Poinsettia before and after planting

 The management of poinsettias before and after they are harvested has a great impact on the quality and shelf life of poinsettias. Proper management can enable sellers to provide customers with high-quality poinsettias that can be stored for a long time throughout the Christmas season. The shelf life of poinsettias is now much longer than it was 20 years ago, but even so, if the storage environment after harvest is not good, the shelf life will still be shortened.

Possible problems of poinsettia after it leaves the field include: falling leaves and bracts, falling flowers, drooping leaves and bracts, yellowing leaves, browning of bract edges, and mechanical damage during transportation. If production, transportation, and sales are properly coordinated, these problems can be basically eliminated or their severity can be greatly reduced.

Poinsettia production practices can affect shelf life. Keeping light intensities high until bracts mature will help prevent bud drop before sale. Too close planting, high night temperatures, or dry substrates can cause immature bud drop, so care must be taken to avoid these conditions. High levels of soluble salts in the soil late in the growing season can cause browning of bract edges and leaf drop after transplanting. Flushing with water before transplanting can reduce soluble salt levels, but be aware that excessive irrigation can also cause permanent root damage, resulting in poor quality and leaf drop. In addition, if using a slow-release fertilizer, it is best to use a release cycle of 90 to 110 days and apply only once at transplanting, so that the fertilizer is almost used up by transplanting.

Poinsettias must be fully developed before they can be transplanted. Lowering the temperature to 13 ℃ to 15 ℃ in the late planting period can make the bracts color better. There are many varieties of poinsettias now, even if some bracts are not fully developed, the bracts are already very red. But if they are transplanted and moved indoors at this time, the bracts will easily fade. Therefore, when transplanting, it is necessary to ensure that the bracts are fully expanded and colored, and the flowers have begun to bloom. Mature poinsettias should be placed in a cool environment as much as possible, but the temperature should not be lower than 10 ℃ -12 ℃. Because lower temperatures will cause the bracts to turn blue or white.

During transportation, the plants should be bagged and boxed to prevent mechanical damage. However, bagging will cause the ethylene released by the poinsettia plants to accumulate, causing the leaves and bracts to droop. The longer the plants are bagged, the more severe the drooping of the bracts and leaves will be, so the packaging must be removed immediately upon arrival. The transportation temperature should be kept between 12 °C and 18 °C. If the temperature exceeds 18 °C, the drooping of the leaves and bracts will be aggravated. Generally speaking, after removing the bag, the plants are placed in a bright environment with a temperature between 18       and 23 °C, and the plants will recover after 24 to 48 hours. The longer the poinsettia stays in the bag, the more time it takes to recover. If the time is too long, some drooping leaves and bracts cannot be recovered. Therefore, the transportation time should be as short as possible, preferably not more than three days.

After the goods arrive, the packaging should be removed quickly. If they are dry, they must be watered thoroughly. A more suitable sales environment helps to maintain the quality of poinsettia. If the temperature of the display environment is 22 ℃ or above, the light intensity is required to be 1100 lux for 12 hours a day , which can reduce the yellowing and falling of leaves; if the temperature is between 18 ℃ and 21 ℃, a light intensity of 550 lux is also acceptable. The environment should be well ventilated, but direct wind should be avoided from blowing directly onto the plants. Do not place the plants directly in the sun; avoid placing them too densely, because too dense will cause the leaves to not receive enough light and increase the amount of leaf fall. For some varieties with larger bracts, it is particularly important to have a certain display area, because the large bracts will block the leaves below and prevent the leaves from getting light; maintain a certain soil moisture to avoid leaf fall, but be careful not to water too much.

19. Poinsettia Pests and Control

 Poinsettias are attacked by a variety of pests, the most common of which are whiteflies, fungus gnats, thrips, spider mites and scale insects. The best way to prevent pests is to completely prevent them from entering. Therefore, if conditions permit, install insect screens in all places that are not blocked from the outside environment, such as vents and doors and windows. Foreign plant materials should be placed in the greenhouse only after they are observed to be free of pests. In addition, there must be timely and effective supervision and detection methods to achieve timely detection and effective prevention and control.

1. Whitefly

Whitefly adults are about 1.5 mm long, white, and covered with wax powder. They can lay eggs 1-3 days after emergence, mostly on the back of tender leaves, usually 60-80 eggs. The eggs are oblong, light yellow, and 0.2-0.5 mm long. The eggs hatch into larvae in about a week, and the eggs turn black before hatching. There are 4 instars in total. The first instar larvae can crawl on the back of the leaves for a short time, but lose their crawling function after entering the second instar, and fix on the back of the leaves to suck plant juice, causing serious damage. The third instar larvae molt into pupae, called " pseudo-pupae " , which is actually the fourth instar larvae wrapped in the hard skin shed by the third instar larvae. Later, the adult breaks out of the " pupa " shell from the "T" -shaped crack to emerge. The life cycle from egg to adult is about 21 to 36 days, which is determined by the temperature of the greenhouse. Adults and larvae gather on the upper back of leaves and suck juice with their piercing-sucking mouthparts, causing poor plant growth, fading, yellowing, wilting, and even death of leaves. At the same time, they secrete a large amount of honeydew, which contaminates the leaves. Honeydew often causes fouling, interferes with photosynthesis, and reduces plant vitality. Whiteflies rarely harm poinsettias, but in severe cases, they can greatly affect the ornamental value of poinsettias.

The key to controlling whiteflies is to avoid the formation of large populations, so some methods should be taken to monitor the trend of whitefly populations. Whitefly adults are attracted to bright yellow, so yellow sticky insect traps are very useful for detection. As whitefly infestation becomes a serious problem in greenhouse production, many whitefly control drugs have appeared in various places, such as " Buscillin " and " High-efficiency Dagongchen " , which can be tried. It should be noted here that before using a new drug on a large scale, it is necessary to conduct a drug damage test first to confirm that the dose used will not cause drug damage to the plants before using it on a large scale.

In addition to chemical control, whiteflies can also be controlled by biological methods. The natural enemy of whiteflies, the entomophilus aphid wasp, is used to parasitize the eggs and pupae of whiteflies, making them lose the ability to reproduce. This method is widely used abroad, and the entomophilus aphid wasp has been sold as a commodity, but it has not yet been widely popularized.

2. Fungus Gnat

Fungus gnats are small dark grey or black flies, about 30mm long. They are often found flitting around on the surface of the growing medium or on leaves. Adults do not usually harm plants directly. Eggs are scattered on the surface of the growing medium and hatch in about 5 to 6 days to become larvae with white translucent bodies and shiny black heads. Larvae usually live in the upper regions of the root system, feeding on decaying organic matter and living plant tissue, thus causing direct damage to the plant. Feeding wounds also allow root pathogens to enter. The transition from egg to adult takes about 2 to 4 weeks. Yellow sticky papers are also effective against adult fungus gnats. Adults are also sensitive to most insecticides and can be controlled by spraying. Larvae can be controlled by soil dredging.

 In addition to fungus gnats, there is another type of fly called shore flies . They are very similar in size and appearance to fungus gnats. Adults have nearly black bodies, red eyes, and white spots on their wings. They can be found in the same places as fungus gnats, so it is easy to confuse them. However, both adults and larvae of shore flies feed on algae and rarely cause damage to plants.

 3. Red spider:

Spider mites are a common greenhouse pest. They do not usually attack poinsettias, but occasionally they can cause problems, especially under hot conditions. Because spider mites are small and reproduce quickly, they are often found in large colonies. Feeding wounds can cause spots on the leaves. Large colonies form webs that are easy to spot and can even completely encase leaves and flowers. The development from egg to adult takes about 7 to 14 days. This depends on the temperature. A hot, dry environment is ideal for spider mites to develop.

Many insecticides are effective against spider mites. Since most spider mites are found on lower leaves, be sure to spray the entire plant evenly from top to bottom when spraying with insecticide.      

4. Thrips:

Thrips are small, slender insects about 1-2 mm long that can be found on leaves or flowers of almost all greenhouse plants. Unless there is a large population of thrips in the greenhouse, thrips are generally not a serious threat to poinsettias.

Thrips feed on leaves and flowers, deforming them. Deformed leaves and flowers are evidence that thrips are or have been causing damage. If thrips feed on growing points, damage will not be noticed until the parts have unfolded, by which time the thrips have flown away. Thrips lay their eggs in plant tissue, which hatch into small yellow larvae that feed on plant sap. Severely infested leaves will appear silvery-grey. The life cycle from egg to adult is about 7 to 13 days. Thrips are very difficult to control, especially if they are found in large colonies. Therefore, it is important to monitor the presence and changes in the number of thrips. Yellow sticky papers are effective against adult thrips, but blue and white sticky papers are more effective.

20. How to schedule poinsettia flowering

Poinsettia has become one of the main potted flowers in the domestic market. Its flowering period is mainly during Christmas, New Year's Day and Spring Festival. The blooming time of Poinsettia is mostly fixed. If you want Poinsettia to bloom at the scheduled time, you must carry out scientific maintenance according to its characteristics.

    1. Matrix:

The optimum pH range of the poinsettia substrate is 5.5-6.0 . The potting substrate can be made of 2 parts of garden soil, 1 part of leaf mold and 1 part of compost, or 3 parts of peat, 1 part of perlite and a small amount of base fertilizer.

    2. Water and fertilizer management:

Poinsettia leaves are relatively sensitive and can easily fall off if not managed properly.

In spring and winter, water less to prevent leggy growth. In summer, water once in the morning and evening , with the principle of "alternate dry and wet". Water after the pot soil is dry, and prevent the pot soil from being too dry or too wet. Fertilizer should be applied with decomposed sesame paste residue. Apply it to the pot surface in May when the new buds grow, and then loosen the soil; apply it again in early June . Apply liquid fertilizer once a week in June and July , and stop fertilizing during the high temperature in midsummer. Fertilize once a week after September until before flowering. Phosphorus fertilizer can be applied during flowering to make the flower buds colorful. Do not water too frequently during the flowering period, and control the temperature to extend the flowering period.

    3. Environmental control:

The optimum temperature for poinsettia growth is 25-29 degrees Celsius during the day and 18-19 degrees Celsius at night . It requires sufficient sunlight. In the shade, it often has weak stems, thin leaves, and pale yellow leaves. Poinsettia is a typical short-day plant, and it can be made to bloom earlier through short-day treatment. For example, if you start shading for 4 hours a day in early August , after 45-50 days of treatment, it can bloom on November 1st.

21. Professional poinsettia seedling production

  1. Conditions required for specialized poinsettia seedling production:

( 1 ) It is necessary to obtain foreign agency rights.

Although the issue of seedling agency rights has not received enough attention in China, since the varieties of poinsettia are controlled by several large foreign companies, if they are not produced legally, they cannot really obtain technical support and the latest varieties, and they cannot produce high-quality seedlings, nor can they carry out real promotion and publicity. Therefore, domestic poinsettia seedling suppliers should actively strive for foreign agency rights to maintain the true vitality of their brands and sustainable development space.

( 2 ) It is necessary to have specialized production equipment and a professional technical team. Healthy and consistent seedlings are the key to standardized production. The production of poinsettia seedlings requires strict control of environmental factors, and also has high requirements for production technology and management level. From the selection of mother plants, environmental control to the prevention and control of pests and diseases, every link requires very strict requirements. If any link is not done well, the number of inferior seedlings will be greatly increased. It is impossible for a seedling supplier without a professional technical team to obtain high-quality seedlings. In addition, since the equipment specifically used for seedling production is expensive, seedling producers should pay attention to large-scale and specialized production.

( 3 ) Have an excellent technical guidance team.

The evaluation of a seedling supplier does not lie in how many seedlings it can sell, but in whether it can make the growers who buy its seedlings gain more profits in the end. At the same time, a good seedling supplier not only means being able to supply good seedlings, but also must be able to provide growers with a complete set of technical support suitable for national conditions, including cultivation substrates, fertilizer supply, cultivation technology and training, door-to-door guidance and other after-sales services. These training and guidance technicians must affirm the experience of successfully planting poinsettias in China, rather than just inviting a few foreign experts to talk or reading a few books to deal with customers. At the same time, a good seedling supplier should have its own demonstration base, so that it can continuously accumulate first-hand cultivation experience, digest and absorb foreign advanced technologies, observe foreign new varieties, and provide training demonstrations for customers.

 2. Several ways to produce poinsettia seedlings in China 

At present, there are several ways to produce poinsettia seedlings in China:

( 1 ) Most of them are old varieties from the 1960s and 1970s. Some of them are mixed with varieties from the late 1980s that were popular in the past few years, such as "Peter's Star", "Angel", "Da Xi", etc. Due to years of self-preservation, producers often do not know the names of the varieties, and often call them American varieties, German varieties, etc. The price of such seedlings is between 0.5-2 yuan. Producers do not know the origin and name of the varieties. The cuttings are taken from plants that have been there for many years. They are specially supplied to producers of low-end poinsettia potted flowers. The current market is still good, and due to the low cost, there is still a certain profit margin.

( 2 ) Keep the potted flowers that were not sold last year as mother plants. Since the variety name of this type of seedlings is clear and the seedlings are not kept for a long time, the quality is much higher than that of the first type of seedlings. And from the appearance of the seedlings, they are even similar to high-quality seedlings. The market price of this type of seedlings is about 2-3.5 yuan, and if the producer is lucky, it may be sold at a price of more than 4 yuan. However, since this type of mother plant is not professionally produced, the quality cannot be guaranteed. Its disease resistance, branching and bract size are all poor. Although it is still profitable at present, it will eventually affect the quality of the finished product, resulting in customer complaints and affecting the reputation of the producer. Therefore, large seedling companies should be particularly cautious.

( 3 ) A few domestic companies have obtained the agency rights of well-known foreign poinsettia seedling companies and have become specialized seedling producers. As foreign seedling companies have seen the huge market potential, after a few years of waiting and observing, they have now seized the market. Foreign companies have officially entered the market through their legal agents. The real competition will take place among these large foreign companies. Such producers receive the latest foreign information and technical support and guidance, and strictly follow the international technical requirements for poinsettia seedling production. They are also subject to strict quality control by foreign authorized companies. To ensure the reputation of the authorized companies, seedling quality requirements must meet the approval of the authorized companies before they can be sold. At the same time, such producers can usually provide customers with after-sales technical services. Such seedlings are new varieties and their quality fully meets international standards. Their prices are slightly lower than imported seedlings, usually between 4 and 5 yuan. However, due to the large initial equipment investment and after-sales service costs and the fact that domestic high-quality seedling brands have not yet been established, the current profits are not high. However, as the brand is established and the demand for high-quality seedlings increases, there will be great room for profit.

( 4 ) The quality of imported seedlings is relatively good, and the price is about 6 yuan. They are generally imported from direct producers in some European countries through domestic trading companies. The varieties that enter the market through this channel include many varieties that were produced abroad in the early years but are not popular abroad in recent years. New varieties are difficult to enter the market due to intellectual property restrictions, and these foreign trading companies do not monitor the quality of seedlings as strictly as professional seedling companies. The quality of seedlings is unstable and there is no after-sales service. It is also difficult to claim compensation when encountering inferior seedlings.

22. Christmas Flower Poinsettia

[Alias] Christmas flower ivory red poinsettia  

【Family】EuphorbiaceaeEuphorbia 

【Origin】Originated from Mexico

[Morphological characteristics] Poinsettia is a deciduous shrub with a ring-shaped inflorescence unique to the Euphorbia genus. The leaves under the inflorescence are "flowers", making it a beautiful ornamental plant in winter. It is grown in pots in Beijing. The leaves can be used as medicine to dissipate blood stasis and reduce swelling. The main types of poinsettia cultivated in Beijing are as follows:

Ipomoea acuta: The characteristic is that the top bracts are white.

Yipinfen: The characteristic is that the top bracts are pink.

Poinsettia: The bracts at the top are red.

Double-petaled poinsettia: The stamens and pistils of this species are both degenerate, and the involucre is covered with multiple layers of red bracts. The leaves are broader and shorter than those of the single-petaled species, and it has a higher ornamental value.

23. New Excellent Pot Flower Poinsettia

　Poinsettia belongs to the Euphorbiaceae family. Because of its brightly colored bracts and high ornamental value, it is now widely cultivated in China and has become a new major annual flower variety in recent years. Not long ago, a German company launched a batch of new varieties. Among these poinsettia varieties, there are the bright red varieties that are common in China, and the two-color varieties that are still rare in China. Among them, the two-color variety 'Avantgarde '  is particularly eye-catching, with pink and white bracts, which are in sharp contrast. Pink is the main color, and white is an embellishment, which leaves a deep impression. Another highlight of this variety is its leaves, which are not just pure green like other varieties, but are covered with beautiful patterns, with different colors of deep or light, and rich layers. In terms of cultivation, this variety has moderate resistance and flower buds are easy to induce. It has a long flowering period, good shelf performance, and is also resistant to transportation.