Key Technical Points for Greenhouse Cultivation and Management of Water Spinach

Water spinach, originally named Yongcai, also known as tengtengcai, wengcai, wengcai, tongxincai, wuxincai, wengcai, kongtongcai, zhuyecai, bears white trumpet-shaped flowers and has a hollow center in its stem, hence the name “water spinach”. It is commonly cultivated as a vegetable in rural areas of southern China.

Water spinach is a trailing plant with a shallow fibrous root system and strong regenerative capacity. The stem is trailing, round and hollow, tender, green or light purple, with a stem diameter of 1-2 cm. The stem has nodes, and each node, in addition to axillary buds, can also produce adventitious roots. The internode length is 3.5-5 cm, with the longest reaching 7 cm. The cotyledons are opposite, horseshoe-shaped. The true leaves are alternate, with a smooth surface, entire margins, very pointed tips, reticulate veins, and a prominently raised midrib. The leaves are lanceolate, long ovate, or heart-shaped. The leaf width is 8-10 cm, with the widest reaching 14 cm, and the leaf length is 13-17 cm, with the longest reaching 22 cm. The petiole is relatively long, about 12-15 cm, with the longest being 17 cm. It is hollow and concave. The fruit is a capsule, nearly round, and the seeds are dark brown, with a 1000-grain weight of 32-37 g. Water spinach is propagated by seeds or tender stems, with seeds used in the north.

Greenhouse Cultivation and Management Techniques for Water Spinach

1) Sowing and Seedling Raising

① Seedbed preparation: For the seedling bed, apply 20 kg of sifted decomposed farmyard manure and 50 g of diammonium phosphate per square meter, spread evenly, shallowly till, rake level, and water thoroughly.

② Sowing period: In North China, sowing for the early spring crop in solar greenhouses can generally be done in early February.

③ Seed soaking and germination: Soak the seeds in warm water at about 30°C for 12 hours, remove and drain excess water, and germinate at 30°C. Rinse twice daily with warm water at 25-30°C, drain excess water, and continue germination. Sprouting occurs in 2 days, and full germination in 3 days.

④ Sowing: It is best to soak and germinate the seeds before sowing. For direct sowing, use a row spacing of about 35 cm and a hole spacing of 15-18 cm for hole sowing, with 3-5 seeds per hole, using 37.5-45 kg of seed per hectare. For broadcast sowing, use 150 kg of seed per hectare. If raising seedlings with thinning for market, use the broadcast method with 30 kg of seed per hectare, requiring 750-900 sq m of seedling bed. After hole sowing or broadcast sowing, cover with about 1 cm of soil.

⑤ Post-sowing management: After sowing, raise the solar greenhouse temperature as much as possible, to 30-35°C during the day and above 15°C at night, and maintain soil moisture. Seedlings emerge 5-7 days after sowing. When seedlings are about 3 cm tall, begin to intensify fertilizer and water management. Urea and other chemical fertilizers can be applied with irrigation water to keep the soil moist and nutrients sufficient; avoid soil drought. Maintain a daytime temperature of 25-30°C. At 30-40 days after sowing, when seedlings are 20-23 cm tall, they can be thinned for market or harvested for market. To accelerate stem and leaf growth, spray 20 mg/L gibberellin, or Baoshi (5 mL in 50 kg water), or Yunda-120 (10 mL in 30 kg water) during the growing period, once every 7-10 days, for 2-3 consecutive sprays. 

2) Transplanting

① Fertilization and land preparation: Choose sandy loam with good permeability, apply 60000 kg of high-quality barnyard manure per hectare plus an appropriate amount of phosphorus and nitrogen fertilizer, plow and harrow fine, then make beds 1-1.2 m wide.

② Transplanting: For seedling transplanting, about 30 days after sowing, generally when seedlings are 17-20 cm tall, transplant at a row and plant spacing of 35 cm, with 3-4 plants per hole, or at a plant spacing of 18 cm with 2 plants per hole. 

3) Field Management

① Temperature management: Water spinach production should maintain as high a temperature as possible. Generally, do not ventilate when the greenhouse temperature does not exceed 35°C. When the temperature exceeds 40°C, ventilate appropriately around noon, and keep the minimum nighttime temperature above 15°C. To promote water spinach growth during low-temperature periods, add small arched tunnels inside the solar greenhouse for extra warmth.

② Fertilizer and water management: After transplanting, intensify fertilizer and water management, mainly with quick-acting nitrogen fertilizer, but the amount should not be too large. Generally, apply about 150 kg of urea per hectare each time. About 30 days after transplanting, when plants are about 33 cm tall, harvesting can begin. Thereafter, harvest once every 7-10 days. After each harvest, intensify fertilizer and water management, with nitrogen fertilizer as the main topdressing, applying 150 kg of urea per hectare each time, while keeping the soil moist to promote the emergence and growth of new shoots. 

4) Harvesting

For those harvested by thinning for market, pull up the whole plant with roots, trim off the roots, and bundle them up. After thinning or transplanting, the pinching harvest method is generally adopted: for the first harvest, when plants are about 33 cm tall, leave 9-12 cm at the base and harvest the tender shoots above. Afterward, new shoots grow from the leaf axils, and when the new shoots reach 15 cm, the next round of harvesting begins. However, for the first 2-3 harvests, leave 2-3 leaves at the lower part to promote more new shoots and ensure high yield. Afterward, leave 1-2 leaves when harvesting to prevent excessive new shoots, weak growth, and reduced yield and quality. During the growing period, also promptly thin out excessive and dense branches from the base to achieve renewal and maintain a reasonable population. For direct sowing with a single harvest, the yield is 15000-22500 kg per hectare; for multiple harvests, the yield can reach more than 75000 kg per hectare.