Water Convolvulus,Chinese Water Spinach, Swamp Cabbage, Kang Kong,
Ipomea aquatica is a member of the Convolvalaceae (morning glory) family. Ipomoea raptans is a similar although lesser known plant.
The plant's smooth-surfaced leaves are either arrowhead-shaped, 5-6 inches long, or relatively narrow and pointed. Two major cultivar forms are grown. These being: Ching quat, the narrow leaved form most often grown in moist soils and Pak Quat, the arrowhead shaped form usually grown in aquatic conditions.
The plant is an herbaceous perennial aquatic, semi-aquatic plant of the tropics and sub-tropics. Alternate branches and leaves arise at the leaf axils of the trailing vine-like stems. The stems being hollow are adapted for floating in aquatic environments. Adventitious roots readily develop at nodes when in contact with moist soil and water. The succulent foliage and stem tips are light green in color. Flowering is favored by short days with the development of white and light pink flowers. Purple flowers develop in wild forms of Ipomoea aquatic. To obtain seed harvesting of the plants is stopped to allow developing flowers to mature, from which seed bearing pods form.
Other names. Kankon (Japanese); ung choi (Cantonese Chinese); toongsin tsai (Mandarin Chinese); ong choy, ungtsai, tung choy (China); kang kong (Filipino, Malaysian); kang kung, rau muong (Vietnamese); pak bung (Thai).
Marketing. Rapid and careful postharvest handling is required to minimize damage to the fragile crop especially due to wilting.
Use. Practically all parts of the young plant tissue are edible although the shoot tips and younger leaves are preferred. Coarse stems and leaves are often used for animal feeding. The tender shoot tips and leaves are eaten fresh or lightly cooked as with spinach. Cooking in oil is common, the addition of spices enhances the relatively bland flavor. These plant greens provide the nutritional benefits of most green leafy vegetables. [Sweet potato shoots tips and leaves sometimes substitute for water convolvulus.]
Climatic requirements.The plant is a frost-sensitive perennial with essentially no growth below 10 C (50 F). Optimum temperatures for growth are between 24 to 30 C (75 to 85 F).
Cultural Practices. "Aquatic" or "production in moist soils" are two cultural methods used. With the moist soil procedure, raised beds are usually used. Seedlings or stem cuttings are transplanted into these beds. Some use is made of directly sown seed at relatively close spacings 10 to 15 cm (4 to 6 inches) in order to maximize the yield of tender shoots and leaves with the resultant growth intended to climb onto trellises that help to maintain continuing productivity and quality. The crop is harvested several times as shoot re-growth readily occurs.
In the aquatic procedure, stem cuttings, about 30 cm (12 inches) having many (7 to 9) nodes are transplanted into puddled soil which is prepared similarly to that for paddy rice culture. The cuttings are placed about 15 cm (6 inches) deep in rows about 30 cm (12 inches) apart. Following transplanting the field is flooded with water that is continuously flowing. Water is maintained at a shallow, 5 cm (2 inches) depth and as growth increases, the water level is also slightly increased. Flooding assists in control of some weeds. The crop is responsive to supplemental fertilization.
Growth is usually rapid with harvest beginning in 4 to 5 weeks. With the semi-aquatic (moist soil) procedure, crop development is somewhat less rapid.
Sunrise Enterprises, P.O. Box 10058, Elmwood, Conn. 06110-0058
Tsang and Ma, P. O. Box 5644, Redwood City, CA 94063
Yamaguchi, Mas. World Vegetables. AVI Publishing Company, Inc. Westport, Conn. 1983. 415 pp.
Figure 1. Chinese water spinach growing in San Diego. (Photo by Hunter Johnson).
Figure 2. Water spinach vine tips bunched for market. (Photo by Hunter Johnson).
Author: Vince Rubatzky, Vegetable Specialist, UC Davis