Management Methods and Technical Key Points for Growing Chinese Toon in a Greenhouse
Chinese toon (Toona sinensis) is a woody vegetable, and its tender leaves are edible. Only when the average temperature over a ten-day period reaches 15°C do the young buds begin to sprout and unfold new leaves. Therefore, open-field Chinese toon in the central part of our province has a harvest period in mid-April. Greenhouse production of Chinese toon involves moving the stems of 1- to 2-year-old Chinese toon that have already dropped their leaves into a greenhouse, planting them at very high density, and providing a certain amount of temperature and moisture to make them sprout, then successively harvesting the unfolded tender leaves. To grow greenhouse Chinese toon well, the following 5 key steps should be carried out:
1. Select Chinese toon with thick stems and plump terminal buds and plant it in zones
When Chinese toon has thick stems, large and plump buds, and sufficient stored nutrients inside, the yield of new leaves it sprouts will be high. Therefore, before planting greenhouse Chinese toon, seedlings should be selected. When heavy frost arrives, the leaves of open-field Chinese toon naturally fall off, and after the nutrients flow back into the stems, dig them out and grade them. One-year-old seedlings are 0.6-1 m tall with a stem diameter above 1 cm; two-year-old seedlings are 1-1.5 cm tall with a stem diameter above 1.5 cm. After lifting the seedlings, grade them according to height. Seedlings 1-1.5 m tall are grade one, 0.8-1 m are grade two, and 0.5-0.8 cm are grade three. When planting, according to the greenhouse's characteristic of being lower in the south and higher in the north, plant grade-three seedlings toward the south, and plant grade-one and grade-two seedlings in the middle and northern parts respectively.
2. Make full use of the greenhouse space for very high-density planting
Planting Chinese toon in a greenhouse is actually a kind of “heel-in”. Only with high density will leaf yield increase and benefits be good. Depending on seedling size, the requirement is to plant 80,000-100,000 seedlings per mu. Seedlings from more than 10 mu of land are needed to supply 1 mu of greenhouse. When planting seedlings, open trenches 30 cm deep in an east-west direction, stand the Chinese toon in bundles in the trenches, and backfill soil to bury the root system. Every 3-4 trenches, leave a 45 cm wide walkway for leaf harvesting and management. After planting, water once to settle the roots. The planting site generally does not need base fertilizer, because the sprouting and growth of Chinese toon buds mainly rely on nutrients stored in the stems, and after leaves unfold they are harvested promptly, basically not using nutrients from the soil. As long as the soil is moist and the air humidity is around 90%, it is sufficient. During the growth period, no topdressing or foliar spraying of fertilizer is needed.
3. Do a good job of cold protection and heat preservation in the greenhouse
After leaf drop, Chinese toon buds begin to sprout only when a temperature of about 25°C is available, and this temperature must remain stable for no less than 10 hours per day; an ordinary greenhouse can hardly meet this requirement. Therefore, a heating flue must be added in the middle of the greenhouse in an east-west direction for heating. In addition, to save coal, a 50 cm thick layer of corn stalks should also be placed on the outer side of the greenhouse wall. The back slope of the greenhouse should also be covered with old straw mats to reduce heat loss. In addition, the thickness of the straw mats on the front roof should not be less than 4 cm. When covering with mats, adjacent mats should overlap by 15-20 cm in width. After putting down the mats at night, a rainproof film should also be added over the straw mats. This not only provides heat preservation but also prevents rain and snow from soaking the straw mats and affecting their insulating performance.
4. High-temperature sprouting promotion and variable-temperature management
To promote faster sprouting of terminal buds, after planting, heating is needed all day so that the room temperature stays at 25°C-30°C. After the terminal buds begin to sprout, lower the temperature appropriately: keep the daytime temperature at 23°C-25°C and the nighttime temperature at 12°C-15°C, with a day-night temperature difference of no less than 10°C, to prevent stems and leaves from growing too quickly, which would make the leaves thin, pale in color, bland in taste, and lower in quality.
5. Make full use of greenhouse facilities to change one crop per year into two or three crops. The harvest season of greenhouse Chinese toon is mainly in winter, that is, from January to mid-March of the following year. At this time, dig out the Chinese toon stems and plant them at 6,000-8,000 plants per mu. After they survive, promptly cut the stock 10-15 cm above the ground to promote sprouting of buds below the cut, strengthen management after the weather warms, and after leaf drop in winter move them into the greenhouse to continue harvesting leaves. In general production, the leaf harvesting period is often extended to the end of April, causing the nutrients stored in the stems to be exhausted. If the seedlings are moved out of the greenhouse in early March and base fertilizer is applied promptly, another crop of early-maturing vegetables such as cucumber, tomato, pepper, and beans can also be planted in time.