Detailed Explanation of the Key Points of Water Spinach (Ong Choy) Cultivation Techniques

Water spinach, also known as bamboo-leaf vegetable, ong choy, or vine vegetable. Convolvulaceae, Ipomoea, annual or perennial herbaceous plant. The tender stems and leaves are stir-fried or used in soup, rich in various vitamins and mineral salts, and it is a very important vegetable in summer and autumn.
I. Biological Characteristics
Water spinach has a fibrous root system, shallow roots, and strong regenerative capacity. The early-maturing type has short stem nodes, with stems flat-round or nearly round, hollow, dark green to light green. The aquatic type has long internodes, easily produces adventitious roots at the nodes, and is suitable for cutting propagation. The cotyledons are opposite, horseshoe-shaped; the true leaves are alternate, long ovate, with the basal leaves cordate or lanceolate, entire margins, smooth leaf surface, dark green, with petioles. Cymes, 1 to several flowers, corolla funnel-shaped, complete flower, white or light purple. Ovary two-celled. Capsule, containing 2-4 seeds. Seeds nearly round, thick coat, dark brown, 1000-seed weight 32 g-37 g.
Water spinach prefers warmth and moisture, tolerates light, and tolerates fertilizer. It has strong growth vigor, and its greatest feature is tolerance to waterlogging and high temperatures. It can grow under conditions of 15°C-40°C and tolerates continuous cropping. It has low soil requirements and wide adaptability; it can be planted in dry land, paddy fields, ditch edges, and field corners. It can still grow in hot summer high temperatures, but it is not cold-tolerant; when frost occurs, the stems and leaves wither and die. In high-temperature frost-free areas, it can be cultivated year-round. Water spinach is a high-temperature short-day crop. In the Yangtze-Huaihe River basin, seed water spinach can flower and set seed. However, vine water spinach has strict short-day requirements and cannot flower or set seed in the Yangtze-Huaihe River basin, so it can only be propagated vegetatively.
II. Types and Varieties
Water spinach is divided into two types: seed water spinach and vine water spinach:
1. Seed water spinach: propagated by seeds, with stronger drought tolerance than vine water spinach; generally planted on dry land, but some are also aquatic. Seed water spinach is further divided into two types: white-flowered and purple-flowered.
(1) White-flowered seed water spinach: flowers white, stems relatively thin, leaves large, response to daylength slow, strong adaptability, crisp and tender texture, high yield, cultivated throughout the country. Examples include Guangzhou Dagguqing, DajiHuang, and Wenzhou ong choy, suitable for shallow-water planting. Zhejiang Longyou ong choy is suitable for water-surface cultivation.
(2) Purple-flowered seed water spinach: flowers purple, stems slightly purple, poorer quality, smaller area, such as Hubei Honggeng bamboo-leaf vegetable.
2. Vine water spinach: propagated by stems and vines, generally few flowers, and even harder to set seed. The texture is tender, quality is relatively good, the growth period is long, and the yield is higher. It is mainly cultivated in paddy fields or marshy land, and can also be cultivated on dry land. Examples include Hunan vine water spinach, Sichuan vine water spinach, Guangzhou tong cai, and Jiangxi water spinach.
III. Cultivation Techniques
Seed water spinach is raised as seedlings in spring; seeds are sown after soaking and sprouting, emerge uniformly, and grow rapidly. Generally, 3 kg-4 kg of seeds are needed per mu (1 mu = 667 sq m). The seedbed can be dry land or paddy field; for early sowing, protected seedling raising is needed in early to mid-March. When seedlings are 15 cm-20 cm tall in early to mid-April, they are transplanted. Row spacing and plant spacing are 15 cm-20 cm square, with 2-3 plants per hole. Besides direct seeding propagation, seed water spinach can also be propagated by picking vine cuttings, inserting the stems diagonally into the soil 4-5 nodes deep, 6 cm deep, leaving 2-3 nodes with leaves exposed above the ground, planting 4000-5000 holes per mu, watering once a day, and surviving after 3-4 days. Vine water spinach can be propagated by direct cutting, indirect cutting, or by divisions from last year's perennial roots.
Cultivation methods are divided into three types according to terrain: dryland cultivation, aquatic cultivation, and floating cultivation (also called deep-water cultivation). Dryland cultivation means planting in an ordinary vegetable garden. Paddy field cultivation can be done in rice fields or low-lying vegetable gardens. Floating cultivation uses ponds, ditches, or riverbanks with thick, fertile mud layers and water depth above 30 cm; in April-May, side branches are taken, clamped with straw rope, palm rope, or thin bamboo poles, with both ends looped over bamboo or wooden stakes, so that the water spinach on the rope floats on the water surface as the water rises and falls, and the stems and leaves produced are crisp and tender.
The management principle for water spinach is early planting, heavy fertilization, and frequent harvesting. Generally, when the plant height is 25 cm-30 cm, harvest by leaving 2-3 nodes at the base; after side branches appear, harvest leaving 1-2 nodes. 2-3 days after each harvest, when the wounds have healed, apply one topdressing of manure water. Water spinach is planted once and harvested many times, with a long harvest period from April to October. Generally, dryland cultivation can yield 2500 kg-3000 kg per mu, and floating cultivation can yield 6000 kg-7500 kg.
IV. Seed Production Methods
Seed production methods for water spinach differ depending on whether it can set seed. Vine water spinach is generally propagated vegetatively, while seed water spinach is propagated by seeds.
1. Vine water spinach. Tender stems should not be selected; instead, select robust stems and vines in the field for seed production, harvest the stems and vines before frost for storage, force sprouts and raise seedlings from the Spring Equinox to Qingming the following year, and cut and plant in the field at Xiaoman or Mangzhong. During storage, dry the stems and vines slightly in the sun, line the bottom of the storage pit with grass, place the stems and vines inside, and cover with rice straw for warmth to help them overwinter safely.
2. There are three seed collection methods for seed water spinach:
(1) Direct harvesting in place: after early-sown water spinach has been harvested 2-3 times, in June select healthy plants in the field that conform to the variety's characteristics as mother plants, stop harvesting, and after the Start of Autumn they flower and set seed; after the seeds mature in November, collect the seeds.
(2) Transplanting for seed production: for those aiming at seed collection, fertilizer and water should not be excessive, to prevent excessive stem and leaf growth. In June, transplant the selected mother plants to high, dry land so that the plants grow compactly, flower abundantly, and set fruit well; harvest when the seeds mature in November.
(3) Cutting for seed production: in June, select superior mother plants from early-sown fields, take cuttings of vines about 33 cm long, and insert them in the seed-production plot with row spacing 66 cm and plant spacing 33 cm-50 cm, 2 vines per hole; after 2 months they can flower and set fruit abundantly. With this method, the seeds are plump and full, and the quality is better than the previous two methods. 75 kg-90 kg of seeds can be harvested per mu.