Detailed Explanation of Key Technical Points for Foliar Fertilization of Orchids

Foliar fertilization of orchids has the characteristics of using a small amount of fertilizer, being absorbed quickly, and being highly targeted. It plays a very important role in preventing and treating nutrient deficiency symptoms and in enhancing the growth vigor and disease resistance and cold resistance of orchid plants. So how much do you know about the specific methods of foliar topdressing for orchids? This article explains the techniques of foliar fertilization for orchids.

1. Types of Spray Fertilizers

Like other plants, orchid growth must first satisfy the need for the three nutrient elements nitrogen, phosphorus, and potassium, but trace elements such as calcium, iron, zinc, magnesium, copper, boron, and molybdenum are also indispensable. Fertilizers commonly used for foliar spraying of orchids include, for nitrogen: urea, ammonium sulfate, ammonium nitrate; for phosphorus: superphosphate, potassium phosphate, potassium dihydrogen phosphate; for potassium: potassium nitrate, potassium chloride; for calcium: superphosphate; for iron: ferrous sulfate; for zinc: zinc sulfate; for magnesium: magnesium sulfate; for copper: copper sulfate; for boron: borax, boric acid; for molybdenum: molybdic acid.

2. Spray Fertilizer Concentration

For foliar fertilization of orchids, it must be carried out according to a certain ratio to ensure both good fertilizer efficiency and no fertilizer damage. The spray concentration varies with different fertilizer types and is generally as follows: urea 0.2%, potassium dihydrogen phosphate 0.3%, potassium sulfate and potassium nitrate compound fertilizer 0.1%, superphosphate 0.5%, magnesium sulfate 0.5%, ferrous sulfate 0.5%, zinc sulfate 0.1%, copper sulfate 0.2%, borax and boric acid 0.3%, molybdic acid 0.1%. In addition, fertilizers such as Yiduo, Yuanshuo, Shida, Lanjunwang, and Penshibao must be prepared and applied according to the product instructions.

3. Spraying Site

For foliar spraying of orchids, the key site must be the underside of the leaves. This is because the upper side of the leaf is covered with a shiny cuticle layer, and the fertilizer solution is not easy to enter. The underside has no cuticle layer and bears many stomata, so the fertilizer solution is easy to penetrate and be absorbed. However, when spraying, the whole plant must be sprayed, that is, all parts other than the orchid roots: leaf surfaces, petioles, leaf sheaths, and pseudobulbs above the soil surface. For orchid plants placed on the ground, when spraying fertilizer, the orchid pot must be laid on its side and rotated one full turn, so that the fertilizer solution can reach every surface and promote balanced growth of the orchid plant.

4. Timing of Spray Fertilization

For foliar spraying of orchids, during the period of new bud and new root growth, apply once every 7-10 days, for 2-3 consecutive applications. From flower bud formation to before flowering, apply once about every half month. During other growth periods, apply 1-2 times per month; during the vegetative growth period, apply more nitrogen and potassium fertilizers, and during the reproductive growth period, apply more phosphorus and potassium fertilizers. The time for foliar spraying must be determined according to whether the weather is cloudy or clear, the temperature level, and the humidity level. When the temperature is between 18-25°C, the stomata of orchid leaves are fully open, and spraying fertilizer at this time has the best effect. When the temperature is below 15°C, because the temperature is low, the stomata of the leaves close or open very little, and the fertilizer solution is not easy to absorb. When the temperature is above 30°C, because the temperature is high, the leaves are scorched, and spraying fertilizer will also cause fertilizer damage. When the air humidity is high, the fertilizer solution stays on the leaves for a long time, and the nutrients absorbed are also the greatest. The best time for spraying fertilizer is on a windless sunny or cloudy day, and early morning or evening is even better. At the same time, attention must also be paid to not applying fertilizer in severe cold, not applying in extreme heat, not applying on rainy days, not applying at noon, and not applying during the flowering period.