Chinatown's produce stands offer many items that make only fleeting seasonal appearances, often so brief that many intrepid chefs scarcely have time to figure out how to cook them properly before they disappear for another year. One example is Water Spinach, a common vegetable in Asian cuisine.
Commonly called Water Spinach, Kangkong or Ong Choy, Ipomoea aquatic goes by many names around the world. With spinach-like leaves with long hollow stems, indeed the Mandarin for water spinach is Kong xin cai，which literally means ‘empty-hearted vegetable’. Almost all parts of the young plant are edible, but the tender shoot tips and younger leaves are preferred. The spinach-like leaves are mild and tender and without any trace of the oxalic acid taste of regular spinach and the long hollow stalks have the advantage of holding onto all flavourings they are cooked with and stay crunchy even when wilted. No wonder it is one of the most popular greens in southeast Asia.
Water Spinach is an herbaceous semi-aquatic perennial plant. This cultivar Ching Quat is usually grown in moist soils, often in beds. Direct seed or transplants may be used. In warmer locations, it can be grown as a perennial. In cool to cold locations, it can be grown as an annual or as a greenhouse plant. It does very well in hydroponic systems and is an excellent permaculture plant.
It grows so fast and easily, and tastes so good, that anyone in a temperate climate could grow this plant indoors in winter and outside in summer.
Water Spinach does not do well where average temperatures drop below 10°C (50°F), and do much better when the temperature is between 20 to 30°C (68 to 86°F). It tolerates very high rainfall, but not frost. For most of us this means we will use Water Spinach as an annual or grow it in a greenhouse.
Water spinach can be grown outside in summer. In cool areas, it can be grown in unheated greenhouses in summer, but will require heated greenhouses for a spring crop.
In moist soil culture, the crop is usually grown on raised beds 60 to 100cm (24 to 39in) wide.
It can tolerate a wide range of soil conditions and does very well in hydroponic systems. The most suitable soil pH ranges from 5.5 to 7.0.
It prefers full sun but where summer temperatures are very high, it is sometimes grown as a ground cover beneath climbing plants. Water spinach should be sheltered from strong winds.
Soak seeds for 24 hours before sowing to encourage germination. Seeds can be sown directly or seedlings transplanted into the beds. Soil temperature requirement for germination is 20°C (68°F).
To produce strong seedlings, seed should be sown 5mm (¼) deep in trays with potting mix deep enough to allow the plants to develop a good root system. Transplant when plants are 10 to 15cm (4 to 6in) tall with four true leaves.
Plant stems are not strong, but plants grown in beds support each other and produce longer stems with less branching. Highest yields are obtained by spacing plants at 15 x 15cm (6 x 6in) They can also be grown in rows about 30cm (12in) apart.
Water spinach needs much more water than most other vegetable crops. This increased irrigation can leach out readily available nutrients, so it is recommended to use slow-release forms of fertility. Where rainfall is low, frequent heavy irrigations are necessary for high quality shoots.
The plants grow to around 30cm (12in) tall with trailing stems that can grow to 2 to 3 meters (6 to 10ft) long.
If you live in warmer locations, you may need to contain the plants or harvest often to keep it from spreading too much. It has long, jointed and hollow stems, which allow the vines to float on water or creep across muddy ground. Adventitious roots are formed at nodes which are in contact with water or moist soil. Harvesting for human consumption is the best method, by far.
Flowering occurs under short-day conditions and commences from mid-summer onwards.
Harvest 30 to 60 days after sowing, depending on climate and culture, earlier if fully aquatic and later if semi-aquatic. They are best harvested before flowering, harvest in the coolest part of the day to prevent moisture loss and wilting.
Water Spinach can be harvested completely or in a cut-and-come-again manner. Plants are harvested by cutting the stem close to the ground. Shoots regrow readily and growers should get two to three cuttings of water spinach before frost.
Water Spinach is always best when used very fresh. It is very perishable and deteriorates rapidly once picked, and only stores in the refrigerator for about a day or two.
It can be used as fodder for animals, including pigs, chicken and ducks.
Practically all parts of the young plant are edible, although the shoot tips and younger leaves are preferred. The leaves can be used whole, or cut into smaller pieces. Like ordinary spinach, the stems require slightly longer cooking than the leaves.
To cook these greens, just trim off the very ends of the stems and chop up the rest, mixing stems and leaves together. Sauté water spinach with just garlic; simple and tasty.
Botanists are unsure where Ipomoea aquatic, Water Spinach originated, but it likely came from somewhere in eastern India to Southeast Asia. It was first documented as a vegetable in 304 A.D. during the Chin Dynasty.
Currently it is found throughout tropical and subtropical regions around the world, but is a common ingredient in Southeast Asian cuisine. It has grown so prolifically in waterway regions of Florida that it is listed locally and federally as a prohibited plant.
Water Spinach, Ipomoea aquatic is closely related to Sweet Potatoes, Ipomoea batatas and to Morning Glories, Ipomoea purpurea.
Water spinach has different names according to language and dialect. Water convolvulus, Kang cong and Swamp cabbage are some alternative names in English.
It is known in Mandarin as Kong xin cai (empty heart/stem vegetable); Ong tsoi and Weng cai (pitcher vegetable) in Cantonese, Kang kong in Filipino and Malasian and in Japanese as Asagaona (morning glory leaf vegetable).
- Additional Information
Packet Size 1 gram Average Seed Count 20 Seeds Common Name Kong xin cai, Kang kong, Asagaona Other Common Names Bamboo Leaved Water Spinach Other Language Names Wasserspinat Family Convolvulaceae Genus Ipomoea Species aquatic Hardiness Tender Perennial Flowers White Natural Flower Time Summer Foliage Green Height 30cm (12in)