Also known as: water convolvulus, water spinach, swamp cabbage, ong choy, hung tsai, rau muong.
Kang kong is closely related to sweet potato, as well as ‘morning glory’, the climbing plant with large purple flowers that grows as a weed in the warmer parts of Australia. Like its relative, kang kong can escape from cultivation and the plant is considered a weed in some places. However, it is a popular and common vegetable in many parts of south-east Asia.
Kang kong prefers damp conditions, flourishing along the banks of streams and boggy areas. The plant’s long, hollow, pale-green stems float on the water or creep along damp ground. The leaves are darker green and are usually long to heart-shaped, depending on variety.
It is quick to grow—simply break off a piece and put it into damp soil. Yields of 10kg per square metre have been reported in Hong Kong. In a greenhouse it can grow up to 10cm per day when given plenty of water and fertiliser, which is often how it is grown in Australia. This maximises yield, minimises water use, and helps keep the plant clean.
Unlike some other green vegetables, kang kong is not bitter; it has a sweet, mild flavour. The young shoots and leaves are picked before the plant flowers to ensure good quality.
In Vietnam, kang kong is eaten raw as part of a salad or included in soup. Elsewhere it is usually lightly cooked, such as stir-fried with a savoury paste or chillies. The stems should be added first when cooking as the leaves take only a few seconds to wilt.
Kang kong is high in carotenoids, including lutein and pro-vitamin A. It contains significant amounts of calcium and iron. Eaten in large quantities, kang kong can act as a mild laxative.