Soil is one of the essential environmental conditions for the growth and development of flowers. Root systems extend and expand within the soil; as long as the soil layer is deep, well-drained, aerated, has a suitable pH level, and possesses sufficient fertility, flowers can grow and bloom normally. Because the environmental conditions required for the growth and development of flowers vary, including the requirements for the physical and chemical properties of the soil, these requirements also differ from flower species. Therefore, soil treatment techniques are crucial to the success of flower cultivation. Generally, the root systems of potted flowers are confined within the pot. They rely on the limited soil to supply nutrients and water to maintain their growth and development. Therefore, the requirements for the soil are even more stringent.

　　I. Basic Soil Requirements for Flowers
　　There are many types of flowers, and the soil characteristics they require for their growth and development vary greatly. Generally speaking, most flowers require soil rich in humus, loose and fertile, well-drained, and highly aerated. The vast majority of outdoor flowers require a soil pH of around 7.0, while greenhouse flowers require acidic soil.
　　1. Soil Characteristics Required for Flowers
① Good Granular Structure, Good Drainage and Aeration
　　Granular structure refers to the 0.01–5 mm size of humus and minerals bound together in the soil. The granules contain capillary pores for water and fertilizer retention, and larger pores between the granules for drainage and aeration, preventing soil compaction after watering or rain. Poor granular structure often results in heavy, compacted soil with poor drainage, easily leading to root rot, yellowing leaves, and even death in flowers.
② Rich in Humus, Long-Lasting Fertilizer Effect
　　Humus is organic matter formed from the decomposition of plant and animal remains and excrement. The soil is rich in humus and available nutrients, which is beneficial for the absorption of nutrients by the roots of flowers. The main way to increase the humus content in the soil is to add fully decomposed organic fertilizer.
　　③ The pH value should be suitable.
　　Most outdoor flowers require neutral soil, while most greenhouse flowers require acidic soil. The adaptability of plants to the acidity and alkalinity of the environment is determined by the characteristics of the plant's root system. According to the adaptability of plant roots to the acidity and alkalinity of the environment, they are divided into: acid-loving plants; weakly acidic plants; near-neutral (slightly acidic) plants; and weakly alkaline plants. The adaptability range of various plants to hydrogen ion concentration is shown in Table 1-1. The pH value of the soil can usually be adjusted with sulfuric acid and quicklime. Ferrous sulfate can also be used to adjust the pH value of the soil. Industrial waste sulfuric acid is generally used to adjust the pH value to save costs.
　　2. Soil requirements of various flowers
　　⑴ Outdoor flowers
　　① Annual and biennial flowers: They can grow well in well-drained sandy loam and loam, but they do not grow well in clay soil and overly light soil. Suitable soils are deep topsoil, with a high water table, moderate moisture content, and rich in organic matter. Summer-flowering varieties are most susceptible to soil dryness, therefore convenient irrigation and drainage are essential. Autumn-sown flowers thrive in clay loam, such as calendula, cornflower, and lupin.
　　② Perennial herbaceous plants: These have strong root systems that penetrate deep into the soil, requiring a soil layer of 40-50cm. A drainage layer should be laid at the bottom to ensure good drainage. Apply ample organic fertilizer during planting to maintain a good soil structure over the long term. One fertilization can sustain flowering for many years. Generally, perennial herbaceous plants require light, humus-rich loam during the seedling stage. From the second year onwards, slightly heavier clay soil is preferable.
　　③ Bulbous plants: These have very strict soil requirements. Bulbous plants generally prefer light, well-drained loam rich in humus. Loam is also acceptable. Especially desirable is a well-drained gravelly soil with a deep, sandy loam topsoil. However, daffodils, hyacinths, lilies, lycoris, tuberose, and tulips prefer loam.
　　(2) Greenhouse flowers
　　require soil rich in humus, loose and soft, with good aeration and drainage, and the ability to maintain soil moisture for a long time without drying out easily. Generally, most greenhouse flowers require acidic soil.
　　(II) Soil types suitable for flower cultivation
Common soil types used in flower production include: river sand, garden soil, leaf mold, peat moss, pine needle soil, pond mud, turf soil, and swamp soil.
　　1. River sand River
　　sand contains no organic matter, is clean, and has a neutral pH. It is suitable for cutting propagation, sowing propagation, and direct cultivation of cacti and succulents. Generally, heavy clay soil can be mixed with river sand to improve soil structure.
　　2. Garden soil
　　Garden soil is generally the topsoil of vegetable gardens, orchards, bamboo groves, etc. It is relatively fertile and has a neutral, slightly acidic, or slightly alkaline pH. Garden soil tends to harden when dry and has poor permeability. Generally not used alone.
　　3. Leaf mold: Leaf
　　mold is generally formed from the decomposition of tree leaves, vegetable leaves, etc. It contains a large amount of organic matter, is loose and fertile, and has good air permeability and drainage. It is slightly acidic and can be used alone to cultivate clivia, orchids, and cyclamen. Generally, leaf mold is used in combination with garden soil and mountain soil. Generally, fallen leaves of broad-leaved trees (preferably those of poplar, willow, elm, and locust trees that decompose easily) are collected in autumn and winter, mixed with garden soil, and piled up for 1-2 years until the fallen leaves are fully decomposed before sieving and use.
　　4. Pine needle soil:
　　Pine needle soil is the humus formed from the decomposition of pine needles in mountain forests over many years. Pine needle soil is grayish-brown, relatively fertile, has good air permeability and drainage, and has a strong acidic reaction, suitable for azaleas, gardenias, camellias, and other flowers that prefer strong acidity.
　　5. Peat moss:
　　Peat moss, also known as sphagnum moss, is formed from the carbonization of aquatic plants such as reeds by sphagnum moss. In northern regions, brown peat moss is often used to prepare nutrient soil.
　　Peat moss is soft and loose, with good drainage and aeration, and has a slightly acidic reaction, making it an excellent substrate for cuttings. It is particularly suitable for cultivating acid-loving flowers native to the south, such as orchids, camellias, osmanthus, and magnolia.
　　6. Pond
　　Mud: Pond mud, also known as river mud, is generally collected from ponds or lakes in autumn and winter. After drying and crushing, it is mixed with coarse sand, rice husk ash, or other light, loose soil.
　　7. Turf Soil:
　　This is made by digging up the top 10cm of sod from natural pastures or grasslands, layering it, and allowing it to decompose for a year or longer. After sieving to remove stones and roots, it is rich in nutrients and has a slightly acidic reaction, suitable for cultivating plants such as roses, carnations, and dahlias.
　　8. Swamp Soil:
　　This is the topsoil collected after swamps have dried up, making it a good potting soil material. Swamp soil is rich in humus, has long-lasting fertility, and is acidic, but it is prone to hardening and cracking after drying. It should be mixed with coarse sand.
　　9. Rice husk ash
　　, also known as rice husk ash, is the ash formed after burning rice husks. It has a neutral or slightly acidic reaction and contains high levels of potassium. Adding it to the soil can make the soil loose and breathable.
III. Flower potting soil
　　Flower potting soil is artificially composted and fermented. It is generally divided into ordinary potting soil, fertilized potting soil, special potting soil, and burnt mud potting soil.
　　1. Ordinary potting soil
　　In autumn, collect weeds, sawdust, fallen branches and leaves, vegetable leaves, etc. First, lay a 30cm layer at the bottom and water it or add an appropriate amount of human excrement. Then cover it with a 10cm layer of soil. Repeat this process until it reaches a height of about 1.5 meters. Finally, seal the top with soil. After fermentation and decomposition, sift to remove impurities before use. After composting, pay attention to management to avoid rain causing nutrient loss.
　　2. Fertilized Nutrient Soil:
　　Add 10% well-rotted cake fertilizer or 20% animal manure to ordinary nutrient soil. Suitable for most herbaceous flowers.
　　3. Special Needs Nutrient Soil
　　: Add 0.1-0.2% sulfur powder to ordinary nutrient soil, compost for a period of time, then spread it out to allow the sulfur odor to dissipate. This compost has a pH of around 5.5, suitable for acid-loving flowers.
　　4. Burnt Mud Nutrient Soil
　　In autumn, pile plant debris such as withered branches and fallen leaves in layers with garden soil, forming a mound, cover it with soil, and then slowly burn it to produce a yellowish-brown ash. Let it sit for a period of time, then sift it before use. This is suitable for planting fruit-bearing plants such as kumquats and Buddha's hand citrons.
　　IV. Nutrient Soil Preparation
　　1. For annual and biennial flowers in greenhouses, such as primroses, cinerarias, dandelions, and butterfly grass, the nutrient soil for seedlings is: leaf mold: garden soil: river sand = 5:3.5:1.5. The nutrient soil for transplanting is: leaf mold: garden soil: river sand = 2-3:5-6:1-2. 2. For perennial flowers, such as asters and peonies, the nutrient soil can be: leaf mold: garden soil: river sand = 3-4:5-6:1-2 　　. 3. For greenhouse bulbous flowers, such as gloxinias, cyclamen, and bulbous begonias, the nutrient soil
　　can be: leaf mold: garden soil: river sand = 3-4:5-6:1-2.
4. For greenhouse
　　woody flowering plants, such as camellias, Michelia figo, and Magnolia alba, use 3-4 parts leaf mold, mixed with garden soil and an equal amount of river sand, and add a small amount of bone meal.
　　5. For cacti and succulents, use soil: coarse sand = 1:1; for Epiphyllum oxypetalum, Epiphyllum oxypetalum, and Christmas cactus, use leaf mold: garden soil: river sand = 2:2:3. 6. For
　　azaleas, a 1:1 ratio of pine needle soil to well-rotted horse or cow manure is most suitable. 7. For
　　major flowering plants, the recommended soil mix is ​​as follows: for seedlings and cuttings, use leaf mold: garden soil: river sand = 4:4:2; for rubber trees and Cordyline fruticosa, use leaf mold: garden soil: river sand = 3:5:2; for palms and coconuts, use 5 parts garden soil and 2 parts river sand. For bonsai and potted trees: Use an appropriate amount of leaf mold and compost, and ensure 1-2 parts of river sand to facilitate drainage.
　　(V) Soil disinfection:
　　Soil disinfection is essential to prevent soil-borne diseases and pests. Commonly used disinfection methods include:
　　1. Steam disinfection: Where conditions permit, use pipes (iron pipes, etc.) to draw steam from a boiler into a sealed wooden or iron container, and put the soil into the container for disinfection. The steam temperature should be around 100-120℃. The disinfection time is 40-60 minutes. Make some small holes in the iron pipe in the container, and the steam will be ejected from the holes.
　　2. High-temperature disinfection: When planting a small number of plants, you can use a large pot to stir-fry the soil. Stir constantly, and at a temperature of 120-130℃, 40 minutes is sufficient.
　　3. Chemical disinfection:
　　① Formaldehyde fumigation: Pour 400-500ml of 40% formaldehyde into the soil and seal it for 2-4 hours. After disinfection, the soil should be left to dry for 3-4 days to allow the pesticide to evaporate before use. Alternatively, the soil can be irrigated with a 50-fold dilution of formaldehyde, sealed for 24 hours, and then left to dry for 10-14 days before use.
　　② Chloropicrin: This is a highly toxic fumigant that kills insects, rodents, and bacteria, and also controls nematodes. Apply 25 holes/m², 20cm deep, 20cm apart, with 5ml of the solution per hole. Immediately after application, cover the holes with soil, tamp it down, and water the soil surface to slow evaporation. Maintain this for 10 days when the temperature is above 20℃, and for 15 days when the temperature is 15℃. Then, repeatedly till and harrow the soil to prevent the pesticide from affecting plant roots. Wear gloves and a respirator when using chloropicrin.
　　③ 70% pentachloronitrobenzene powder, applied in strips at 2.5-5kg/acre on raised beds and then incorporated into the soil, can also control pests and diseases.