Detailed Explanation of the Key Techniques for Soilless Culture of Orchids Indoors
Orchids are one of China's famous flowers, with a long history of cultivation, and are mostly grown in pots. Orchids have a particularly elegant fragrance and bloom throughout the year. They can not only be used for indoor viewing and decorating rooms, but their roots, leaves and flowers can also be used as medicine, making them widely popular. Soilless culture is a cultivation method that has become popular internationally in recent years. Soilless growing media are light, coarse, and highly hydrophobic and breathable, which can prevent root rot and also avoid mud and sand splashing from watering and fertilizing, which would pollute the environment. The key techniques for indoor soilless culture of orchids are introduced below:
1 Selection of Growing Media
The growing media for soilless culture of orchids can be divided into 2 major categories: organic media and inorganic media. Organic media include rotted tree bark, wood shavings, charcoal, grain husks, etc. They need to be rinsed with clean water, then sun-dried or sterilized at high temperature for 2 hours, then rinsed again and dried for later use. Inorganic media include foamed plastic blocks, foamed plastic strips, perlite, coarse river sand, small stones, etc.; there are also brick and tile pieces and ceramic kiln clay granules (these 2 need to be soaked in water for 24 hours to remove their fiery nature before use), etc. Inorganic media do not need disinfection. Soilless media have low moisture retention, do not contain high nutrients, and easily lose water and fertilizer, which can easily cause poor growth. Some soilless media are hard and often hinder the growth of orchid roots. Therefore, soilless media need to be properly blended. The general formula is: 70% inorganic media, 30% organic media. Alternatively, organic media alone can be used, with the specific formula being: 30% tree materials, 10% stems and leaves, 10% waste residue, 10% seed shells, 40% charcoal.
2 Water and Fertilizer Management
① The substrate for soilless culture generally has poor water retention. To promote orchid growth, an appropriate amount of water should be supplied multiple times daily. The amount of watering depends on light and temperature conditions. In midsummer and golden autumn, when temperatures are high and light is strong, water thoroughly once each in the morning, noon and evening; in late spring and early winter, water once each in the early morning and evening; during the dormant period, water thoroughly once a day. It is best to keep it moist but not wet, dry but not parched. ② The fertilizers for soilless culture of orchids are generally inorganic fertilizers, mainly nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer, as well as some compound fertilizers. For base fertilizer, Magic Fertilizer and Hi-Control can be used. Both are long-acting multifunctional compound fertilizers, with nitrogen, phosphorus and potassium ratios of 3:20:3 and 7:6:7 respectively. Magic Fertilizer is generally applied at about 5 grams per pot, and Hi-Control generally at 3-3.5 grams. Topdressing can be applied to the roots or sprayed on the leaves. Root application should be done in the evening, followed by watering once with clean water the next morning, 3 times a month; foliar spraying is best done at around 9:00 in the morning, using 1 gram of urea and 1 gram of monopotassium phosphate, mixed with 2 kg of water, fully dissolved, and then sprayed on the leaves. Fertilization can be carried out from April to November, and the principle of applying thin fertilizer frequently should be adhered to.
3 Plant Shape Management
After orchids form flower buds, all buds that are poorly developed or of poor ornamental value should be removed to ensure large and beautifully colored flowers; after blooming, the flowers and flower stalks should be cut off together promptly, rather than waiting until the flowers naturally fall off, so as to reduce nutrient consumption and benefit flowering the following year.
4 Sunlight, Temperature and Ventilation Control
According to the growth habits of orchids, orchid pots should be placed indoors with a sunlight rate of 10%-40% and good ventilation, and the temperature around the flower pots should be controlled at 28°C-30°C.
5 Pest and Disease Control
The main pests and diseases of orchids include southern blight, anthracnose, scale insects, red spider mites, etc. The control methods are as follows: ① Southern blight. In soilless culture, because drainage is good, this disease occurs less often. Once it occurs, the growing media can be removed and lime sprinkled on; a 600-800 times dilution of 12% copper abietate emulsifiable concentrate can also be sprayed and used as a root drench, and after 7-10 days, spray and drench once more. ② Anthracnose. Orchids are prone to this disease. It can be controlled by spraying an 800-1500 times dilution of 50% thiophanate-methyl wettable powder, once every 7-10 days. ③ Scale insects. When the population is not dense, they can be brushed off with a soft brush; otherwise, a 600-800 times dilution of essential balm can be sprayed to kill them. ④ Red spider mites. They can be killed by spraying a 150 times dilution of neutral laundry detergent in water, or by spraying a conventional acaricide diluted with water in the prescribed proportion.