I. Introduction
Reproduction is a natural phenomenon that allows offspring to continue. Garden plants are diverse in species and origin, resulting in complex reproductive methods, which can be broadly categorized into sexual reproduction, asexual reproduction, and tissue culture.

II. Sexual Reproduction:
The method by which flowering plants reproduce through their seeds is called sexual reproduction, also known as seed propagation. This involves sowing seeds to obtain seedlings. The advantages are that a large number of plants can be obtained in a relatively small area and in a short time. The method is simple, low-cost, and suitable for large-scale professional production and transportation. It conforms to the natural growth and development patterns of the plants, resulting in complete root systems and robust growth. The disadvantages are the long time from sowing to seed harvesting and the susceptibility of cross-pollination to variation, making it difficult to maintain the superior characteristics of the original variety.

sowing

1. Seed Quality and Storage:
To obtain superior offspring, superior seeds must be selected. Superior seeds should be fully developed, large, and viable, with a high germination rate and vigor. Seeds should be of high purity, free from hybrids, impurities, pathogens, and insect eggs, or treated to be free from pathogens and insect eggs. To obtain good seeds, all imported flower seeds must undergo seed quality testing and origin identification.

To maintain seed germination vigor, germination rate, and lifespan, it is best to store seeds in a dry, sealed container in a cool, well-ventilated place (1-5 degrees Celsius) to reduce seed physiological activity, prolong seed life, and maintain high viability. The principle of seed storage is to keep seed metabolism in a state of minimal activity. The main external influencing factors are humidity, temperature, and air. Therefore, without affecting seed viability, the seed moisture content should be relatively low; this is the so-called standard moisture content for seed storage. Different varieties have different standard moisture contents. Generally, the storage temperature for seeds should be below 15 degrees Celsius, with an ideal temperature range of 0-5 degrees Celsius, and good air circulation is recommended.

2. Seed treatment

Seed treatment can promote early germination and uniform seedling emergence. Since the size, seed coat thickness, and characteristics of various garden plants' seeds differ, different treatment methods should be used to treat them differently.

(1) Seeds that germinate easily: Marigold, cypress vine, and some cactus seeds germinate easily and can be sown directly. They can also be treated with cold or warm water. Soak seeds in cold water (0-30℃) for 12-24 hours or in warm water (30-40℃) for 6-12 hours to shorten the seed expansion time and speed up the germination.

(2) Seeds that are difficult to germinate: Generally, large seeds such as pine nuts, canna lilies, bird of paradise, and lotus flowers are difficult to germinate. Their seed coats are thick and hard, making it difficult to absorb water. For these seeds, the seed coat can be scratched or broken with a knife before soaking. When treating large quantities of seeds, they can be soaked in dilute sulfuric acid. Before use, it is essential to conduct an experiment and control the time carefully. As soon as the seed coat softens, immediately rinse the sulfuric acid off the seed coat with clean water to prevent the sulfuric acid from burning the embryo.

(3) Seeds with slow germination

Some flower seeds, such as coral bean, asparagus fern, clivia, and honeysuckle, germinate very slowly and should be pre-germinated before sowing. Before pre-germination, soak the seeds in warm water until they swell, then spread them evenly on gauze, cover them with a damp gauze, and place them in a constant temperature incubator at 25-30℃. Rinse the seeds with warm water along with the gauze once a day. Sow the seeds immediately after they begin to germinate.

(4) Seeds that need to have their dormancy broken

Some seeds cannot germinate normally during dormancy, even if given suitable conditions such as water, temperature, and oxygen. They must undergo vernalization at low temperatures in order to germinate, flower, and bear fruit, such as peach, apricot, lotus, rose, azalea, and magnolia.

For dormant seeds, low-temperature stratification can be used. The flower seeds are layered and buried in moist, pure sand, then placed in an environment of 0-7℃. The stratification time varies depending on the species, generally around six months. For example, azaleas and flowering plums require 30-40 days, crabapples 50-60 days, peaches, plums, and apricots 70-90 days, wintersweet and white magnolias more than three months, and red pines more than six months. After stratification, the seeds can be removed, the sand and soil sifted out, and then either sown directly or germinated before sowing.

3. Sowing period and pre-sowing preparation

(1) For garden plants with different sowing periods, the sowing period should be selected according to the needs and their own biological characteristics, and according to the environmental conditions.

By flexibly managing the conditions and sowing at the right time, not only can seedlings emerge uniformly and have a high germination rate, but the needs of flower application at different stages can also be met.

The sowing period for annual flowering plants is generally in spring. In northern regions, this is from early April to early May; in the Central Plains, it's from early March to early April; and in southern China, it's from late February to early March. Sowing can be adjusted earlier or later depending on market demand, such as around May Day or National Day. Biennial flowering plants are generally sown after the beginning of autumn. In northern regions, this is mostly in early to mid-September; in southern regions, it's mostly in mid to late September and early October.

For outdoor woody flowering plants, the seeds are mostly large, such as apricot, privet, ash, plum, and peach. Most are sown in autumn from early September to late October, allowing for vernalization in the field and resulting in uniform germination the following year. Sowing too early is not recommended, as the high autumn temperatures can cause the seeds to germinate and become susceptible to frost damage. Seeds that have undergone stratification can be sown in spring, immediately after the soil surface thaws, allowing the seedlings to lignify before the hot summer months, preventing wilting due to excessive rain and high temperatures.

The sowing period for greenhouse flowers: Most greenhouse flowers are evergreen plants from tropical and subtropical regions, such as cacti and evergreen foliage plants. Seed germination is mainly affected by temperature. In a greenhouse, sowing can be carried out year-round, and the sowing time can be arranged according to market demand. It is important to maintain a relatively constant temperature during greenhouse sowing; large temperature differences between day and night often lead to sowing failure.

Most lawn plants can be sown in early spring or autumn, with autumn sowing generally being the best option. Before sowing, the soil must be thoroughly watered. Sowing can also be done in summer, but high temperatures can cause poor seedling growth, and the presence of weeds can sometimes lead to sowing failure.

(2) Pre-broadcast preparation

a) Soil Preparation: The soil used for seedling cultivation is the foundation for supplying the water, nutrients, and air needed for seedling growth and development. High-quality seedbed soil should be fertile, loose, and fine-grained. For seedlings with small seeds, the requirements for the soil are more stringent, and the soil particles should be small. The formula for this nutrient soil is as follows:

Formula (1) — 50% garden soil (pond mud), 25% wood ash (or coconut coir, peat), 25% well-rotted chicken manure (or other well-rotted organic fertilizer).

Formula 2 – 40% garden soil (pond mud), 25% wood ash (or coconut coir, peat), 10% fine sand, 25% well-rotted chicken manure (or other well-rotted organic fertilizer).

b) Soil disinfection

For disinfection, use 60 grams of 65% mancozeb powder per cubic meter of bed soil. After mixing, cover with a thin film for 2-3 days. After removing the film, wait until the smell of the pesticide dissipates before use. This method has a certain control effect on diseases.

Chloropicrin disinfectant is effective against all soil-borne pests and diseases. The optimal application temperature is 15-20℃, and the seedbed soil should be slightly moist. Before application, mound the seedbed soil to a height of 30 cm. Insert a small hole every 30 cm, 10-15 cm deep, and pour 5 ml of chloropicrin into each hole. Seal the holes and cover the mound with a plastic film. After approximately 7-10 days, remove the film, thoroughly turn the soil to allow the odor to dissipate, and the seedbed soil can be used after another 7-10 days.

Methyl bromide disinfection has a certain killing effect on soil-borne pests and diseases. Pile the seedbed soil into a 30 cm high long pile, level the surface, and place a small basin in the center of the pile. Add methyl bromide and cover with a perforated lid. The dosage is 100-150 grams per square meter of seedbed soil. Seal the pile with a small arched shed to prevent the pesticide from evaporating and overflowing. After 10 days, remove the shed, turn over the seedbed soil, and after another 2-3 days, once the pesticide odor has dissipated, the seedbed soil is ready for use.

c) Seed disinfection: Seed disinfection can effectively prevent seedling diseases, such as damping-off and seedling blight, thereby improving the seedling survival rate. Common disinfection methods include the following:

For seed treatment with carbendazim powder and trichlorfon powder, the dosage should be 0.2-0.3% of the seed weight. It is best to dry mix the seeds to ensure even coating and reduce the risk of phytotoxicity.

For disinfection with formalin solution, seeds are usually soaked in a 200-fold dilution of 40% solution for 10-15 minutes, then rinsed, dried, and sown.

For disinfection with copper sulfate solution, soak seeds in a 1% copper sulfate solution for 5 minutes, then rinse, air dry, and sow.

For disinfection with potassium permanganate, soak seeds in a 0.5% potassium permanganate solution for 2 hours, then rinse, air dry, and sow.

3. Sowing methods and procedures

(1) Sowing method　

Broadcasting involves evenly scattering seeds on the seedbed. This method is suitable for small seeds. If the seeds are too small, they can be mixed with an appropriate amount of fine sand before sowing. Broadcasting yields a large seed quantity, produces many seedlings, and saves labor and land, but it requires a large amount of seeds and is more difficult to manage.

Sowing by digging holes at a certain plant spacing is suitable for large seeds and relatively rare seeds, such as ginkgo, pine, and rare cactus seeds. Sowing by digging holes is labor-intensive and time-consuming, but the seedlings are robust and easy to manage.

Row sowing involves planting seeds in furrows at a certain row spacing. It is suitable for medium and small seeds. The row spacing and sowing width are determined according to the situation. Row sowing requires less seed and is easy to manage. This method is mostly used for woody seedlings.

(2) Sowing procedure

Sowing should be done using appropriate methods depending on the size of the seeds and specific circumstances.

Cover the seeds with soil promptly after sowing, ensuring the soil layer is 2-4 times the seed diameter. Some extremely small seeds, such as those of begonias, gloxinias, and certain cacti, may not require covering, but must be covered with glass or plastic film to retain moisture after sowing. Use loose soil, fine sand, wood ash, coconut coir, or peat moss for covering; avoid heavy, clay-like soils.

Rolling helps to tightly bind the seeds with the soil, allowing them to fully absorb water and swell, thus promoting germination. Rolling should be done when the soil is loose and the topsoil is relatively dry. Heavy, clayey soil should not be rolled, as this may hinder seed germination. Seeds that have been pre-germinated should not be rolled.

After sowing, cover the soil with plastic film, shade netting, etc. to maintain soil moisture, prevent rain, and regulate temperature. However, the covering should be removed promptly after the seedlings emerge.

e) Watering: The potting soil should be thoroughly watered before sowing, but no watering is needed before emergence. If some seeds have a long germination period and require watering, spray irrigation should be used to avoid direct watering, which can cause the seedbed to compact. If seeds are sown in pots, the soaking method can be used until the surface of the soil in the pot is moist.

4. Post-sowing management

Moisture, atmosphere, and temperature are key factors affecting seed germination. Under suitable temperature and good sowing soil conditions, seedlings will emerge with proper management. From sowing to emergence, the soil should be kept moist, and watering should be even. Container sowing with glass to maintain humidity can generally keep the soil moist until germination. If some seeds require up to 7 days to germinate, or if the weather is particularly dry, water can be provided again. The glass should be opened in the morning and evening to allow ventilation. In early summer and even summer, when temperatures are high and seed germination is rapid, the glass can be left uncovered to prevent seedling rot and death caused by excessive temperature and humidity. In autumn and winter, when temperatures are low and seed germination is slower, the glass must be covered during the day to effectively prevent moisture evaporation. Temperature control is particularly important in autumn, when temperatures often fall too low, prolonging germination and affecting the emergence rate. Therefore, effective insulation, or even heating devices, is necessary to meet the temperature requirements for seed germination at all times. After the seeds germinate, remove the covering immediately to allow the seedlings to gradually receive sunlight. After a period of hardening-off, they can be placed in full sunlight. Fertilize once after the true leaves appear. Transplant the seedlings when they have 4-5 true leaves; these are commonly called seedlings. Some seedlings can be transplanted when they have 1-2 true leaves in the pot. Use the same pots as for sowing.

III. Asexual Reproduction

Asexual reproduction is a method of propagation that utilizes the regenerative capacity of plant vegetative tissues with artificial assistance; it is also known as vegetative propagation. Common asexual reproduction methods for flowers include cuttings, grafting, division, and layering. Their advantages include maintaining the superior traits of the parent plant, a short growth cycle, and earlier flowering and fruiting. However, a disadvantage is that some flowers may not grow as vigorously or as well as seedlings grown from seed.

Propagation by cuttings

Cuttings are one of the important methods of flower propagation. Thanks to the application of certain technologies in flower production, almost all plants, from annuals and biennials and cacti to conifers, can be successfully propagated by cuttings. Propagation by cuttings involves inserting the plant's vegetative organs, such as roots, stems, or leaves, into a substrate, allowing them to root and sprout into complete plants. Its advantages include abundant propagation material, high seedling yield, rapid seedling establishment, early flowering, and preservation of the original variety's inherent superior characteristics. It yields seedlings with genetic traits completely identical to the mother plant, making it suitable for both large-scale production in flower farms and small-scale home propagation. The disadvantages are that the resulting cuttings have poorer root systems, cannot form a taproot, have a shorter lifespan than seedlings, and are less resistant to disease than grafted seedlings.

1. Methods of propagation by cuttings: Depending on the material used for cuttings, propagation by cuttings can be divided into stem cuttings, leaf cuttings, leaf-bud cuttings, bud cuttings, and root cuttings. These methods are suitable for various garden plants in the process of propagation by cuttings.

(1) Herbaceous cuttings Among herbaceous cuttings, chrysanthemums are the most commonly used. Cuttings of herbaceous flowers should be selected from the branch tips at the bottom of the plant. For example, the best cuttings of chrysanthemums are the young shoots that grow directly from the roots, generally about 6 cm long. The tissue should be of moderate maturity. Too young and it is easy to rot, too old and it will root slowly. When cutting cuttings, it should be done below the node, because the roots that grow from the adventitious buds on the node are better than the roots that grow from the callus tissue at the cut.

Leaf cuttings utilize the callus tissue generated from wounds created on the veins of a leaf, which then sprouts adventitious roots or buds, thus forming a new plant.

For the flat-laying method, take a mature leaf from a begonia or gloxinia, cut off the petiole, and first make cuts on the main veins on the back of the leaf with a blade. Then lay it flat on a sand surface and press it down with small stones to ensure close contact between the main veins and the sand surface. Maintain humidity at the same time. After about one month, roots will sprout from the cuts, and new leaves will also emerge from the same point, while the old leaves will gradually wither. To reduce evaporation, the edges of the leaf can be trimmed (see Figure 3-1-1).

The direct insertion method involves cutting the leaves of the snake plant into small sections, each 4-6 cm long, and then inserting them shallowly into plain sand. After a period of time, fibrous roots will develop from the base wounds, and underground rhizomes will grow. A new plant will grow from the terminal bud of the rhizome (see Figure 3-1-2).

For cuttings of plants like African violets and gloxinias, take leaves with petioles and insert them into pure sand, keeping them at a suitable level of humidity. This method promotes rapid root development, with new plants emerging from the petioles. Seedlings grown using this method are more robust than those grown by placing the plant horizontally.

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Figure 3-1 Schematic diagram of leaf cuttings, leaf bud cuttings, and root cuttings of flowers

1. Begonia cuttings (horizontal cuttings) 2. Snake plant leaf cuttings 3. Rubber plant leaf and bud cuttings 4. Camellia leaf and bud cuttings

5. Chrysanthemum leaf bud cuttings 6. Hydrangea leaf bud cuttings 7. Peony and Paeonia suffruticosa root cuttings

Scales of lilies can be used for propagation by cuttings. After the lily flowers have faded, dig up the bulb, dry it for several days, peel off the scales, and insert them one by one into a sand bed. After 40-60 days, small bulbs will be produced at the base of the scales.

f) Softwood cuttings: When propagating herbaceous flowers by softwood cuttings, the tips of stems with terminal buds are often used as cuttings to facilitate root development and growth, especially for those plants that do not easily sprout lateral buds. Herbaceous plants such as chrysanthemums, carnations, dahlias, wandering jew, petunias, salvia splendens, coleus, and begonias can all be propagated by cuttings (see Figures 3-2-1, 2).

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Figure 3-2 Schematic diagram of softwood cuttings for several types of flowers

1. Geranium 2. Chrysanthemum 3. Rose 4. Cacti

g) Leaf bud cutting: Leaf bud cutting is performed by cutting off a small section of branch along with a node before the axillary bud matures and becomes plump but has not yet sprouted. The bud is then inserted shallowly into a sand bed, with the tip of the axillary bud exposed above the sand surface. When adventitious roots develop at the base of the petiole, the axillary bud begins to sprout and then grows into a new seedling (see Figure 3-1-5).

h) Root cuttings: Some flowering plants with large, fleshy fibrous roots or taproot systems, such as peonies, can be propagated by root cuttings. New plants grow from adventitious buds that sprout from the roots. Root cuttings are usually carried out in spring and autumn when transplanting or dividing the mother plant. Roots with a diameter of 0.5-1.5 cm should be selected and cut into sections of about 10 cm. Thicker roots can be planted obliquely in the soil, while thinner roots should be placed flat on the surface of the seedbed and covered with 1 cm of fine sand (see Figure 3-1-7).

(2) Woody Plant Propagation: The main propagation method for woody flowers is stem cutting, which is further divided into softwood cutting and hardwood cutting. These are described below:

Softwood cuttings, also known as greenwood cuttings, are taken from semi-lignified, leafy branches during the vigorous growth period of summer and autumn. Select well-developed, semi-lignified branches from the current year's growth, remove any overly tender tips, and cut them to about 10 cm in length, retaining 1-2 leaves at the top, which can be trimmed by 1/2-2/3. Then, using a sharp knife, make a clean cut 1.5-3 mm below the base node, being careful not to strip the phloem, and immediately insert the cuttings into moist substrate. Keep the cuttings moist to prevent wilting and subsequent failure (see Figure 3-2-3).

Hardwood cuttings should be taken from fully lignified one- or two-year-old branches, with leaves and petioles removed. Hardwood cuttings are usually taken during the dormant period after leaf fall and before bud break the following year; in southern regions, this is often done in autumn, while in northern regions, it is often done in spring. Cuttings are generally 10-20 cm long, with the cut end 0.5-1 cm away from the terminal bud to prevent it from drying out. Most of the cutting can be inserted into the substrate, leaving only 1-2 lateral buds. Shading is generally not required after cutting. Special treatments can be applied to the cuttings during the process, such as splitting them, including a soil ball, or including a small section of a lateral branch (with a heel). (See Figures 3-3-1, 2, 3).

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Figure 3-3 Several special hardwood cutting methods

1. Split insertion 2. Root ball insertion 3. Heel insertion

In addition, rubber trees among woody plants can also be propagated by leaf cuttings (see Figure 3-1-2), while camellias, peonies, azaleas, osmanthus, rubber trees, and gardenias can be propagated by leaf bud cuttings (see Figures 3-2-3, 4, 6). Chinese toon, lilacs, flowering quince, and wisteria can be propagated by root cuttings (see Figure 3-1-7). The operating methods are the same as in the previous section.

(3) Cactus and succulent plant cuttings

Propagating cacti and succulents by cuttings differs from that of herbaceous and woody plants, and has its own unique characteristics. If the technique is not mastered properly, the plants are highly susceptible to rotting. Cactus and succulent propagation utilizes the strong regenerative ability of their vegetative organs, which can produce adventitious buds or roots. A stem segment or part of a stem segment, along with any offsets or adventitious buds, is cut and inserted into the substrate, allowing it to root and develop into a new plant.

Types and methods of material collection

Some species readily produce offsets, and these offsets often have roots already attached to the mother plant. In such cases, the offsets can be easily separated and planted directly. The *Gymnocalycium mihanovichii* (long-lasting cactus) is an example of this.

Some varieties also easily produce offsets, but these offsets do not root on the mother plant and can be separated for propagation by cuttings. Examples include *Gymnocalycium mihanovichii*, *Gymnocalycium chinense*, and *Gymnocalycium chinense*.

Species with fleshy, segmented stems can be propagated by cuttings at the nodes. Examples include Christmas cactus, Christmas finger cactus, epiphyllum, and pencil cactus.

For spherical varieties that do not readily produce offsets and columnar varieties that do not easily branch, top cutting is necessary at the beginning of the growing season. This involves cutting the plant at an appropriate point, allowing the upper section to dry before propagation by cuttings, and then providing intensive care to the lower section to encourage offset production. Examples include Golden Barrel Cactus and Snow Barrel Cactus.

Some species can be propagated by leaf cuttings using robust leaves. Examples include Kalanchoe blossfeldiana, Bryophyllum kalanchoe, Echeveria elegans, Pyrite spp., and Jade Plant.

Some species of the Kalanchoe genus in the Crassulaceae family, such as Kalanchoe pinnata, can produce bulbils at the leaf margins. These bulbils can be removed and directly inserted into a pot to grow into new plants.

2. Environmental conditions for rooting cuttings

Cuttings root more easily when the temperature reaches 20-25℃, but for species of the genus Gastrodia elata native to tropical regions, a slightly higher temperature is more suitable.

Because cacti contain a lot of water, they do not require high humidity when propagating by cuttings. In particular, the cutting substrate should not be too wet, otherwise it will easily rot.

After sun propagation, the cuttings should be properly shaded to avoid direct sunlight.

The most suitable substrate is a well-draining and moisture-retaining material. Cuttings can be directly inserted into well-draining soil. Other commonly used cutting materials include river sand, rice husk ash, peat moss, leaf mold, sawdust, and coal ash, which can be used alone or in combination.

3. Cuttings period

In South China, cuttings can be taken year-round, but spring and autumn are the best times. Summer cuttings are best avoided, as most species are dormant during this season, and the high temperature and humidity can easily cause rotting. When taking cuttings in winter, ensure they are kept warm. In northern regions, spring cuttings are suitable.

4. Precautions and post-cutting management

Use a sharp stainless steel knife when cutting scions, and make a smooth cut. When cutting scions from diseased plants, disinfect the knife with alcohol.

The mother plants used for cuttings should be vigorous and healthy; weak plants are generally not suitable for cuttings.

Cuttings should not be planted immediately after being taken; they must be allowed to dry before planting. Thicker cuttings should be allowed to dry for several more days. Cuttings should not be planted too deep; the base should only be slightly submerged in the substrate.

For some species that are difficult to root, soaking them in a 250 ppm naphthaleneacetic acid solution for 4 hours after the cut ends have dried can promote rooting.

Once the cuttings have rooted, transplant them into pots promptly, keeping the potting soil slightly moist. Do not water for a few days after potting, and provide appropriate shade (see Figure 3-2-4).

(ii) Grafting propagation

Grafting is a major method of propagation for garden plants. It involves combining two different plants together using a propagating material (stem, bud, or bulb) to allow them to heal and form a new, independent individual. The propagating material used for grafting is called the "scion," and the plant that receives the scion is called the "rootstock."

1. Advantages and disadvantages of grafting

Advantages of grafting

(1) Overcome the disadvantage that some plants are not easy to propagate; some garden plants that are not easy to survive by cutting or layering, or plants that cannot maintain their excellent characteristics by sowing, can be propagated by grafting, such as dwarf ornamental peach blossoms and double-petaled plum blossoms.

(2) Maintain the excellent traits of the original variety; since the traits of the propagule used as scion are stable, the excellent traits of the plant can be maintained, while the rootstock generally does not affect the heritability of the scion.

(3) It can improve the resistance of scion varieties; the rootstock used for grafting has many excellent characteristics, which in turn affect the scion, thus improving the scion's resistance to diseases and pests, cold resistance, drought resistance, and tolerance to thin soil. For example, grafting peony onto peony, grafting chrysanthemum onto Artemisia or Artemisia annua, and grafting azalea onto Rhododendron molle can all improve its adaptability.

(4) Early flowering and fruiting: Because the scion is already mature when grafted, the root system of the rootstock is strong and can provide sufficient nutrition, making it grow vigorously and helping to accumulate nutrients. Therefore, grafted seedlings grow stronger and flower and bear fruit earlier than seedlings grown from seed or cuttings.

(5) Change the shape of the plant; by selecting rootstock, seedlings with different plant shapes can be cultivated, such as grafting peach onto dwarfing rootstock, grafting willow onto standard rootstock, and grafting rose onto rose to produce tree roses, etc., so that the grafted plants have special ornamental effects.

(6) Rapid seedling growth: Since the rootstock is relatively easy to obtain, and the scion only requires a small section of branch or a bud, the propagation period is short and a large number of seedlings can be produced.

(7) Enhance ornamental value and promote variation; for cacti, after grafting, the scion's shape is more ornamental than the mother plant due to the mutual influence between the rootstock and the scion. Some grafted varieties have mutated due to the mutual influence of genetic material, resulting in new species. The famous Dragon and Phoenix Peony is a mutated variety that occurred when Scarlet Peony was grafted onto Hylocereus undatus.

Disadvantages of grafting

(1) Limitations: Grafting is mainly limited to dicotyledonous plants, while monocotyledonous plants are more difficult to survive, and even if they survive, their lifespan is shorter.

(2) Labor-intensive and time-consuming; grafting and management require a certain amount of manpower and time, and the cultivation of rootstock requires a certain amount of human resources.

(3) Highly technical; grafting is a highly technical job, and skilled workers need to be trained.

2. Commonly used rootstocks and suitable seasons for grafting

(1) Commonly used rootstock types

Rootstocks can be sourced from two sources: wild seedlings and cultivated varieties with strong resistance. Commonly used rootstocks are listed in the table below.

Table 2-1 List of Commonly Used Rootstocks

scion

Kinuta wood

scion

Kinuta wood

Peach

Longevity Peach

Michelia champaca

Yellow orchid, magnolia

Dragon locust

Chinese scholar tree

Golden Cypress

Chinese arborvitae

plum bossom

Wild apricot, wild peach

White Orchid

Yellow orchid, wood pen

osmanthus flower

Privet, small wax

Magnolia grandiflora

Yellow orchid, magnolia

Golden Tachibana

Other citrus fruits

Midori Kashiwa

Juniper, Chinese arborvitae

Purple cloves

Privet, small wax

Peony

Peony

Five-needle pine

Black Pine

Dragon Juniper

Juniper, Chinese arborvitae

West Azalea

Rhododendron and Azalea

Winter plum

Other wintersweet

chrysanthemum flower

Artemisia annua, Artemisia argyi ...

Cherry blossoms

hairy cherry

cacti

Dragon fruit, grass ball

Magnolia

Mulan

Yunnan Camellia

Wild Camellia

Rose

rose

(2) Suitable season for grafting

Grafting can be done in spring, summer, and autumn, but spring and autumn are preferred. Some varieties grown in greenhouses can be grafted year-round. However, the specific grafting method varies depending on the type of plant and the grafting technique. Generally, branch grafting is done before sap begins to flow, while bud grafting is best done in late summer or early autumn when the axillary buds of the scion have fully developed. Chrysanthemums can be grafted throughout their growing season, while cacti can be grafted year-round.

(3) Tools and materials used for grafting

The rootstock and scion for grafting should be prepared before grafting.

The tools used for grafting include pruning shears, grafting knives, budding knives, hand saws, and blades.

For most woody plants, plastic film is used for binding, which has advantages such as good elasticity, water retention, and ease of use. In addition, for grafting cacti, cotton thread and cotton balls are needed for binding and fixing.

Grafting wax effectively prevents the wound from drying and dying after grafting. Grafting wax can be divided into solid and liquid types. Solid grafting wax is made by mixing rosin, beeswax, and animal oil in a 4:2:1 ratio. First, melt the animal oil, then add the rosin and beeswax together, melt it, and pour it out. After cooling, it becomes solid and needs to be softened by heating before use. Liquid grafting wax is made by mixing rosin, animal oil, alcohol, and turpentine in a 10:2:6:1 ratio. First, heat the rosin and animal oil together in a pot until melted, then remove it, let it cool slightly, add the alcohol and turpentine, stir well, and then store it in a sealed bottle.

3. Grafting propagation techniques for flowers

To improve the survival rate of grafting, different grafting methods are used based on the characteristics of various plants and different growth stages. The main methods are branch grafting, bud grafting, root grafting, and flat grafting. The rootstock is the foundation of grafting; its growth vigor and compatibility with the scion both affect the grafting success rate. Generally, rootstocks must be cultivated in a nursery to meet the needs of grafting propagation.

Selection of rootstock

Since the rootstock has a significant impact on the scion, and there are many types of rootstocks available, the selection should be based on local conditions and the timing. The selection of rootstocks should meet the following conditions:

It has a strong affinity with scions. It generally has a strong affinity with plants of the same genus, such as plum grafting onto apricot rootstock, wild plum rootstock, mountain peach, and hairy peach.

Peach trees are highly adaptable to various environmental conditions, including cultivation areas, climate, and soil. For example, hairy peach trees are highly tolerant of moisture but relatively weak in cold resistance, while wild peach trees are the opposite. Therefore, when selecting rootstock for plum blossoms, hairy peach trees are preferred in the south, while wild peach trees are more commonly used in the north.

Grafting can have a positive impact on the growth, flowering, fruiting and lifespan of scions. For example, grafting plum onto apricot rootstock or plum rootstock results in a longer lifespan than grafting onto wild peach or hairy peach, but the flowering is later.

Abundant sources and easy propagation, such as the rhododendron or rhododendron rootstock used for Western azaleas, have a wide range of sources and a large wild quantity, which can meet the needs of grafting;

It has good resistance to diseases, pests, drought, floods, and low temperatures. Wild rootstocks generally have strong resistance, such as wild peach, wild plum, and rhododendron.

Rootstock cultivation

Rootstocks can be propagated asexually or sexually. However, it is best to propagate rootstocks by seed, as seedlings are more resistant to adverse environmental conditions and have a longer lifespan. In addition, their true age is younger, and they do not alter the inherent traits of superior scions.

grafting methods and steps

(1) Steps of the splicing method (see Figure 2-1)

For scion preparation, one-year-old branches are generally selected, with a length of 5-10 cm and each stem segment containing 2-3 buds. Then, using a grafting knife, two symmetrical bevels of different sizes are cut at the base of the scion. The incision depth should not be too deep, just enough to remove most of the wood. One side should be about 2 cm long, and the other side about 1 cm long. The knife should be sharp, and the hand should be steady to ensure that the cut surface is flat and smooth. It is best to make the cut in one stroke.

Cut the rootstock short at 20 cm from the ground and trim it flat. Then, according to the thickness of the scion, select a suitable position on the north side of the rootstock cut and use a knife to make a slit from top to bottom, about 2.5 cm deep. Be careful to use a sharp blade to ensure the cut surface heals.

Insert the cut surface of the prepared scion into the cut of the rootstock, aligning the cambium layers on both sides. The upper end of the scion should protrude about 0.2 cm, commonly known as "showing the white part," which is beneficial for the scion and rootstock to bond.

Use plastic strips to tightly bind the joint. For some tender scions, in order to prevent the scion from drying out before the joint heals, it is best to cover the scion and the cut with a small plastic bag to reduce moisture loss. Remove the bag after the scion has sprouted new growth.

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Figure 2-1 Cutting steps

1. Cut the scion. 2. Cut the rootstock. 3. Insert and bind the scion.

(2) Steps of the cleft grafting method (see Figure 2-2)

This method is suitable when using a large mother plant as rootstock, that is, when the rootstock is thick and the scion is thin. First, use a cleaver to make a vertical cut about 3-4 cm deep from the center of the rootstock's cross-section. The cut surfaces on both sides of the lower part of the scion should be of equal length, forming a wedge shape of 3-4 cm, leaving 2-3 buds at the top. To improve the survival rate, two scions are usually inserted into the two sides of the rootstock cut, aligning the cambium layers on the outer side of the scion with those on one side of the rootstock, and finally binding them together. Plastic strips can be used for binding, or wax can be applied.

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Figure 2-2 Steps of the wedge joint method

1. Split the rootstock. 2. Prepare the scion. 3. Insert the scion and tie it in place.

(3) Steps of the contact method (see Figure 2-3)

Approach grafting is commonly used for evergreen woody flowering plants, such as privet grafted with osmanthus, Chinese arborvitae grafted with Chinese juniper, and Japanese black pine grafted with Japanese white pine. Approach grafting should be carried out during the peak growing season. First, transport the well-cultivated one- or two-year-old rootstock to the vicinity of the mother plant to be grafted. Select a branch from the mother plant that is similar in thickness to the rootstock, and make a spindle-shaped cut at an appropriate location, about 3-5 cm long and deep enough to reach the xylem. The cut should be smooth, and the cuts on both branches should be the same length. Then, place them together, aligning the cambium layers, and bind them together. After the graft has taken, cut the scion below the graft union and the rootstock branch above the graft union.

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Figure 2-3 Steps of the approach method

1. Cutting the rootstock and scion. 2. Approach grafting and binding.

(4) Steps for abdominal connection (see 2-4)

The preparation of the scion is similar to that of cleft grafting. One side of the scion has a smooth, 2 cm long cut at the bottom, and the other side is cut at a 45° angle. When preparing the rootstock, do not cut it off completely; only make a downward slant cut of approximately 30° near the base to match the size of the scion. Then insert the scion and bind it with plastic film. If it does not take, a second graft can be performed. The rootstock should be cut only after the scion has taken.

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Figure 2-4 Steps of the abdominal connection method

1. Prepare the scion. 2. Cut the rootstock. 3. Insert the scion. 4. Bind the graft.

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Figure 2-5 Subcutaneous grafting procedure

1. Prepare the scion. 2. Cut the rootstock. 3. Insert the scion. 4. Bind the graft.

(5) Subcutaneous grafting procedure (see Figure 2-5)

Bark grafting, also known as bark insertion grafting, is often used when the rootstock is relatively large, with a thick bark that is easy to peel. After cutting the rootstock at an appropriate distance from the ground, a vertical slit is made from top to bottom on the smooth side of the cut, reaching the xylem and about 3 cm long. The end of the scion is then cut into a thin, tongue-shaped surface. The prepared scion, with its larger bevel facing the xylem, is slowly inserted into the bark. To prevent the scion from tilting, the rootstock should be exposed ("white bark"). Finally, it is bound with plastic film.

Bud grafting methods and steps

(1) T-budding (see Figure 2-6)

For bud grafting, select fully mature branches from the current year's growth. Choose plump axillary buds on the scion and remove the leaves, leaving only the petiole. Make a horizontal cut 0.4 cm above the bud, penetrating about 0.1 cm into the xylem. Then, push upwards from 0.5-0.6 cm below the axillary bud back to the horizontal cut. Remove the axillary bud and peel away the xylem inside the bud patch. Wrap the bud patch in a damp towel or place it in your mouth.

To prepare the rootstock, select a smooth bark surface 10-15 cm above the ground on the north side of the rootstock seedling. Make a "T"-shaped incision in the phloem, with its length and width slightly larger than the bud patch. Then, use the handle of the budding knife to pry open the bark.

The bud is inserted into the bark of the rootstock from above the "T" shaped incision, so that the upper end of the bud matches the incision on the rootstock, but the bud and petiole on the bud must be exposed.

Use plastic film to tie the leaves, leaving only the axillary buds and petioles exposed.

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Figure 2-6 “T” budding method

1. Prepare the bud patch. 2. Cut the rootstock. 3. Insert the bud patch into the bark of the rootstock. 4. Bind it.

(2) Embedded budding (see Figure 2-7)

This method is suitable for saplings with thin rootstocks and rootstocks whose bark is not easily peeled off naturally. The survival rate of grafting is not as high as that of "T" budding. There are three types: patch budding, ring budding, and shield budding. When cutting the bud patch, depending on the method and the scion, make a cut 0.1-1 cm above the bud and then 0.5-0.8 cm below the bud. After removing the bud patch, make an incision on the rootstock that corresponds to the size of the bud patch at an appropriate location. Then insert the bud patch into the graft union, aligning the cambium layers on both sides, and finally bind or seal with wax.

root grafting

Root grafting is a grafting method that uses roots as rootstock, generally performed in early spring or autumn when the plant is dormant. This method is commonly used for peonies, roses, magnolias, and trumpet vines. Generally, roots from 1-2 year old seedlings are selected as rootstock. The roots of the mother plant are dug up, and a relatively thick root segment, about 1-1.5 cm in diameter, is selected. The rootstock is washed clean of mud and shaped into a wedge with a clean, sharp knife. The lower end of the scion is then shaped accordingly; scions are generally selected from current-year shoots. During grafting, it is crucial to align the cambium layers. If the scion and rootstock are of different thicknesses, ensure that the cambium layers on one side are aligned. Then, bind the graft with plastic tape and plant it in moist sand. During the growing process, pay attention to shading and maintaining moisture (see Figure 2-8).

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Figure 2-7 Several methods of budding. Figure 2-8 Root grafting.

1. Sheet budding 2. Ring budding 3. Shield budding 1. Scion 2. Rootstock 3. Grafting

Flat joint method

This method is simple, convenient, and has a high survival rate, making it suitable for columnar and spherical varieties. The height of the rootstock can be flexibly adjusted according to different requirements and personal preferences. However, when making a horizontal cut on spherical rootstocks, care must be taken to remove the growing point; otherwise, the scion may be pushed off, causing grafting failure. After the horizontal cut, a portion of the stem flesh and outer bark of the *Hylocereus undatus* or *Hylocereus undatus* is cut off at a 30° angle downwards. This is because after grafting, the fleshy, succulent part at the top of the rootstock will shrink due to water evaporation, but the outer leathery bark will not. When the scion shrinks and sinks along with the rootstock stem flesh, the hard bark of the rootstock will push the scion off, causing grafting failure. Make a horizontal cut at the bottom of the scion and immediately place it on the cut surface of the rootstock, ensuring partial contact between the scion and the vascular bundles of the rootstock, then tie it securely.

When grafting golden needles, the scion and rootstock are often cut at an angle, with the lengths of the bevels roughly the same. They are then fitted together and bound. This method is called oblique grafting, but its operation is similar to flat grafting and will not be described in detail. During grafting, both the rootstock and scion should be cut with a sharp knife to ensure a smooth and clean contact surface. During the rainy season or when cutting scions from rotten or diseased plants, the grafting knife should be disinfected with alcohol before each cut to prevent infection.

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Figure 2-9 Grafting methods for cacti

1. Flat joint method 2. Misaligned joint method 3. Wedge joint method

4. Post-grafting management

(1) Check survival

For branch grafting, check the survival rate 3-4 weeks after grafting. If the scion has sprouted and is bright green, it has survived. For bud grafting, check the survival rate 1 week after grafting. If the petiole remaining on the bud falls off easily when touched, it indicates that it has survived. Otherwise, the bud has died and a replacement should be grafted below it.

(2) Loosen the binding

After grafting, the scion can be untied one month after it has taken root. It's generally not advisable to do this too early, otherwise the scion won't heal firmly and will easily fall off in the wind. It also shouldn't be done too late, otherwise the binding site will become damaged, affecting growth. Bud grafting is usually done in September. After successful grafting, the axillary buds will not sprout again that year, so the binding can remain until early spring of the following year when the buds sprout.

(3) Pruning the rootstock, removing buds, and removing suckers

The timing of rootstock pruning depends on the situation. Grafted seedlings can be pruned in the same year they take root, while most budded seedlings can be pruned 1-2 times in the year of scion emergence. In addition to removing numerous sprouts from the rootstock, excessive sprouts and root suckers on the scion should also be removed to ensure concentrated nutrient supply.

(iii) Division reproduction

Division propagation is one of the methods of vegetative propagation in plants. It refers to the artificial separation of young plantlets, such as suckers, from the mother plant and their subsequent planting to become independent new plants. Division propagation is the simplest and most reliable propagation method, with a high survival rate, but the yield is low. Due to the different biological characteristics of flowering plants, it can be further divided into two methods: division of the plant body and division of the bulb. The former is mostly used for flowering shrubs with strong clumping ability and perennial herbaceous flowers with strong suckering ability, while the latter is used for bulbous flowers.

1. Division method: The division method produces seedlings quickly, and most of them can flower in the same year.

Time for division

(1) Deciduous flowering trees The best time to propagate these flowering trees by division is during the dormant period. In the north, it is usually done in early spring, while in the south, it can be done in autumn after the leaves fall. This is because the air humidity in the south is relatively high, the soil generally does not freeze, and some flowering trees can grow some new roots before winter, and the branches are not easy to dry out in winter.

(2) Evergreen trees do not have a distinct dormancy period, but regardless of whether it is in the south or the north, they mostly stop growing in winter and enter a semi-dormant state. At this time, the sap flow is slow, so they are mostly divided in early spring.

Division method

(1) For some species of open-field flowers and shrubs, the mother plant needs to be dug up from the field before propagation by division, with as many roots as possible. Then the entire clump is divided into several clumps, each with a large number of roots, such as peony and tree peony. There are also some flowering shrubs and vines with strong sprouting ability, which often sprout many small clumps around the mother plant. When dividing, it is not necessary to dig up the mother plant, but only to dig up the sprouts and plant them separately, such as rose, trumpet vine, and rose.

(2) Potted Flowers Division propagation of potted flowers is mostly used for herbaceous plants. Before division, remove the mother plant from the pot, shake off most of the soil, find the direction of each sucker's root system, and separate the roots that are intertwined, minimizing damage to the root system. Then, use a knife to separate the root neck connecting the sucker and the mother plant, and prune the root system, removing old and diseased roots. Then, immediately pot the plant. After watering, place it in a shaded area for maintenance. If wilting is observed, spray water on the leaves and surrounding area to increase humidity. Once new buds sprout, return it to normal care. Examples include orchids, bird of paradise, and daylilies.

(3) Cacti and succulents: Division propagation is rarely used for cacti, except for a few species such as White Sandalwood, Pine Tree, Silver Barrel Cactus, and Velvet Ball. These species easily produce offsets, but the offsets do not have a significant size difference from the mother plant. The offsets have already developed roots on the mother plant, thus forming clumps. When they become too crowded, they need to be divided in time. Generally, they can be separated by hand into several clumps and potted separately. Division can be done all year round in the south, but spring is the best time. In the north, spring and summer are the best times. Division is more commonly used for succulents, such as Aloe, Snake Plant, and Haworthia. There are often many small plants at the base of the plant. These small plants quickly grow to the same shape as the mother plant and develop their own root systems. They can be potted separately in the early stages of growth when repotting.

In addition, some herbaceous plants often have modified stems such as stolons, suckers, and bulbils at the root zone or leaf axils. For example, saxifrage, spider plant, strawberry, lily, and some species of lawn plants have stolons, which can be removed and propagated by cuttings; suckers of aloe vera, pineapple, etc. can be cut off from the mother plant and planted separately; bulbils of kalanchoe, etc., can be removed and planted in soil to root and grow into a new plant.

2. Propagation by dividing bulbs

Most bulbous flowers have a strong ability to reproduce through division of their underground parts, producing new bulbs every year. Propagation using these new bulbs is simple and results in earlier flowering. The methods of bulb division vary depending on the plant organ within the bulb, and can be broadly categorized as follows:

(1) Bulbs: Gladiolus and freesia have bulbs. Gladiolus and freesia have a strong ability to divide. After flowering, while the old bulb dries up, several bulbs of different sizes can be divided. Large bulbs can be planted in the second year and can flower in the same year, while small bulbs need to be cultivated for 2-3 years before they can flower. They can also divide into many small bulbs with a diameter of 0.5 cm. These bulbs can also gradually grow into large bulbs after being sown in rows (see Figure 5-1).

Figure 5-1 Ball-splitting method (Gladiolus)

(2) Bulbs: Bulbs are modified underground stems with a bulbous disc on which thick, fleshy scales grow, giving them a spherical shape. Each year, several offset bulbs grow from the base of the old bulb, clinging to the mother bulb. These offset bulbs are then separated and planted separately to cultivate larger bulbs. Bulbs are classified by the presence or absence of their outer membranous skin: bulbs with skin, such as tulips, hyacinths, daffodils, and lycoris, and bulbs without skin, such as lilies and fritillaria (see Figure 5-2).

Figure 5-2 Bulbous plants (Narcissus)

(3) Tuberous plants are modified stems formed by the enlargement of the stem, which are nearly tuberous, and the buds are usually at the top of the tuber. For example, the underground part of the canna has horizontal tubers and many branches. The growth point is located at the top of the branch. When dividing, each tuber branch must have a terminal bud in order to grow a new plant. New roots develop at the nodes of the tuber. After such tubers are divided and planted, they can all flower in the same year.

(4) Tuberous plants are formed by the enlargement and modification of underground roots. They do not have buds on their tubers; instead, their buds grow on the rhizomes near the ground. Planting a single tuber alone will not produce a new plant. Therefore, each part must include a root neck to form a new plant when it is divided. Examples include dahlias and ranunculus (see Figure 5-3).

Small tubers after dahlia tuber division

Figure 5-3 Root plants (dahlias)

(5) Rhizomes Some plants have large and thick rhizomes with structures similar to above-ground stems, such as nodes, internodes, and buds. Roots can form on the nodes and lateral buds can be produced. After being cut off, they can become new plants. Examples include calla lilies and spider lilies.

(iv) Propagation by layering

Layering is a common propagation method for woody flowering plants that readily root at their nodes and internodes, as well as those that are difficult to root from cuttings. Layering involves making a ring cut or incision at a suitable location on a branch that is still attached to the mother plant. A rooting hormone can be applied, and this wound is then buried in the soil. Because the injured area easily accumulates nutrients and hormones synthesized in the upper part of the plant, roots readily form. The layered branch is then cut off from the mother plant and transplanted to create a new plantlet. Because the xylem of the layered branch remains connected to the mother plant, it continuously receives water and mineral nutrients, preventing it from drying out. Therefore, it is a safe and reliable propagation method. Its advantages include a high survival rate, rapid seedling emergence, and early flowering, requiring no special care. However, its disadvantages include requiring more space and producing fewer seedlings.

Layering can be done year-round in the south, but spring and the rainy season are ideal. In the north, it is mostly done in spring or the first half of the year, allowing ample time for the root system to develop before winter. Under medium or high temperature greenhouse conditions, some flowering trees can also be propagated by layering in winter. There are three main methods of layering: ordinary layering, soil layering, and high-branch layering.

1. Ordinary layering method

Single-branch layering involves bending down a longer lower branch of the mother plant, then making incisions or girdling the bark on the protruding part of the bend. The branch is then buried in the soil and secured with hooked branches or iron bars to prevent it from springing back. The tip of the layered branch should protrude above the soil surface and be fixed with a bamboo pole to ensure upright growth. Layered seedlings grown in spring are cut off from the mother plant in autumn. This method is often used for shrubs and small trees (see Figure 4-1-1).

In the continuous layering method, a longitudinal trench is first dug on one side of the mother plant. Then, the nodes of the branches closest to the ground are scored, and they are shallowly buried in the trench, leaving the tips of the branches exposed above the ground. After a period of time, new roots will sprout from the buried nodes, and soon the axillary buds on the nodes will also sprout and emerge from the soil. Once the newly sprouted old plant has matured, the internodes of each segment are cut deep into the soil with pruning shears. After more than six months of cultivation, it can be transplanted. This method is mostly used for shrubs (see Figure 4-1-2).

Wavy layering is used for some vine-like woody flowering plants, such as winter jasmine, grape, trumpet vine, and Virginia creeper. Their branches are long and flexible, especially the vine-like varieties. After their nodes are buried in the soil, most of them can naturally develop new roots. They can be buried in the soil in a wavy pattern, node by node, without making any marks. Roots will develop in about 20 days. Then, the exposed internodes can be cut off one by one. The water and nutrients absorbed by the new roots at the nodes can be used for the axillary buds to sprout, thus forming many seedlings (see Figure 4-1-3).

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Figure 4-1 Common methods of pressing strips

1. Single-branch layering 2. Continuous layering 3. Wavy layering 4. Soil-embedded layering

2. Soil layering method

Soil layering, also known as mound layering, is commonly used for large, deciduous or evergreen shrubs with strong clumping growth. These shrubs typically lack distinct nodes, have weak branching ability, and lack large, plump axillary buds, such as magnolia, redbud, yellow rose, pearl bush, gardenia, and honeysuckle. In layering propagation, existing branches are used to encourage root development at their base, yielding a large number of seedlings at once. The method involves making a girdling cut at 20-30 cm above the ground on the lower part of the branch during the vigorous growth season in early summer. Then, a mound of soil is built up to bury the lower half of the plant, keeping the soil moist. After a period of time, new roots will grow from the girdling wound. The following spring, the mound is dug up, and the new roots are individually cut off below them, allowing for direct planting (see Figure 4-1-4).

2. High-branch layering method

For some evergreen woody flowering plants that are difficult to root through cuttings, such as those with branches that are not easily bent or short enough to be layered on the ground, air layering can be used for propagation. Examples include citrus, magnolia, milan, jasmine, osmanthus, azalea, camellia, and Buddha's hand. The cuttings are often wrapped with plastic film, half a bamboo tube, or a flowerpot filled with potting soil or peat moss. Perennial branches, preferably two-year-old branches, can be used, or current-year semi-lignified branches. The lower half of the branch should be wrapped. If using a flowerpot, the drainage holes at the bottom should be enlarged beforehand to allow the branch tip to be inserted into the pot without damaging the leaves. Regardless of the material used for the soil, the area to be wrapped should be girdled or scored before wrapping to encourage new root growth. Common scoring methods include:

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Figure 4-2 High-branch layering method

1. Scratching 2. Flowerpot high pressure method 3. Thin film high pressure method

The scoring method involves making several vertical scratches on the pressed area, or making one or two horizontal scratches, reaching the wood. This method is often used for flowers that easily develop roots.

The bark removal method involves carving away one or two tongue-shaped pieces of bark from the pressed area, along with a small amount of xylem. In some cases, a wider ring of phloem needs to be peeled off, and the cambium scraped clean to prevent callus tissue from forming and connecting the severed phloem. In some cases, the xylem at the wound needs to be dried before being wrapped with soil. This is to encourage the cambium above the girdled area to develop new roots. This method is often used for flowers that have difficulty rooting.

The constriction method involves tightly binding a thin wire to the buried area, allowing it to penetrate deep into the xylem and preventing it from thickening. The phloem sieve tubes are also cut off, causing the assimilated nutrients to concentrate there and stimulate root growth.

For some relatively soft flowers that are easy to separate from the bark, the twisting method is often used to improve work efficiency under high pressure. The part to be pressed is twisted by hand to separate the phloem and the wood.

When creating wounds using the above methods, growth hormone treatment can also be used. After air layering, maintain soil moisture. Soil wrapped in plastic film is less likely to dry out; to add water, untie the binding ropes or use a syringe. High-branch layering usually requires more than six months of maintenance before pruning from the mother plant, and then potting it with its original soil (see Figure 4-2).