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Water Spinach, Kang Kung

Ipomoea reptans, I. Aquatica


Also known as water convolvulus and swamp cabbage. This leafy vegetable is prolific in many parts of Asia. The leaves are long and pointed and dark green, the stems paler green and hollow.

Preparation: It should be washed thoroughly as it grows in swampy areas. It may be cooked like spinach, stir-fried with various sauces, or added to soups. To keep a bright colour blanch in boiling water for 30 seconds, refresh in cold water and drain. Add to recipe and toss with flavours for a minute or so.

Often, in Asian shops, the stems alone are sold in plastic bags, looking like pale green corkscrew curls. This is because they have been cut into lengths, split into thin shreds and soaked in cold water to make them curl. The swollen stems split readily, making it a decorative effect that could be achieved at home.

 

Other Languages:
China: ong choy, ung tsai
India: kalmua
Indonesia: kangkung
Japan: kankon
Malaysia: kangkung
Philippines: kangkong
Sri Lanka: kangkung
Thailand: pak boong
Vietnam: rau muong, rau muong che

 

Water Spinach (Ipomoea aquatica) is a member of the Convolvulaceae (Morning glory) family and the same genus as the sweet potato (Ipomoea batatas). Water spinach is an herbaceous aquatic or semi-aquatic perennial plant of the tropics and subtropics. It has a creeping growth habit but may grow erect in water. There are two major cultivars of water spinach. Ching Quat, also known as “green stem” water spinach, has narrow leaves and white flowers and is usually grown in moist soils. Pak Quat, also known as “white stem” water spinach, has arrow-shaped leaves and pink flowers and is grown in aquatic conditions, similar to rice.
Almost all parts of the young plant tissue are edible, but the tender shoot tips and younger leaves are preferred. Other names of water spinach include: water convolvulus, swamp cabbage (English); kankon, you-sai (Japanese); ong tsoi, weng cai (Cantonese); toongsin tsai (Mandarin); kang kong (Filipino, Malaysian); kang kung, rau muong (Vietnamese); pak bung (Thai); batata acquatica, cancon (Portuguese).

Production
Water spinach is a frost sensitive plant. Optimal temperatures for growth are between 75° and 85° F and chilling injury can occur below 50° F. The cultivar Ching Quat is grown in moist soils, often in beds. Direct seed or transplants may be used. Many Asian growers in Massachusetts will soak the seed until germination to ensure the seed is viable. Growers plant in beds with 6 – 10 seeds per foot in rows that are 6 – 8 inches wide. Plant stems are not strong, but plants grown in beds support each other and produce longer stems with less branching, which is what the market prefers.
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. Harvest of the entire plant can be made 50 to 60 days after planting. Plants are harvested by cutting the stem close to the ground and then nitrogen is applied to encourage re-growth. Shoots regrow readily and in Massachusetts, growers will get two to three cuttings of water spinach before frost.
The cultivar Pak Quat requires the same aquatic environment as paddy rice, meaning it can’t be grown viably in New England.
Pests
Tarnished plant bug adults (Lygus rugulipennis) feed on the succulent tissue where new leaves are developing in the leaf internodes. They pierce the tissue and inject a toxin into cells, which causes death of cell tissues, prevents the new leaves from developing, or causes distortion of the emerging leaf as it unfolds. A blackened, dead area at the growing tip is evidence of their feeding.
Tarnished plant bugs also cause holes in the leaves which enlarge with the leaf, often in a somewhat symmetrical pattern on the two halves of the leaf. Damage to the growing tip stops the elongation of the plants and stimulates more branching below. Since the markets prefer a longer-stemmed plant, this effect reduces marketability and delays harvest. Holes in the leaves also reduce the marketability of the greens.

Management of tarnished plant bug should begin with reducing favorable habitat surrounding the production area, including eliminating fallow, weedy areas. Use of row covers can exclude tarnished plant bugs. Insecticide registrations on this crop are limited since it is a noxious weed. Insecticides used should include only materials that have a broad label for all leafy green crops, such as neem.

Other leaf-feeding insects include the golden tortoise beetle (Metriona bicolor) which may be seen as adults which can change from shiny gold-colored to dull rust colored, or the larvae, which have the habit of piling frass on their backs. The spotted cucumber beetle (Diabrotica undecimpunctata howardi) may also be present. Both of these beetles cause chewing injury to leaves, but rarely reach numbers high enough to cause significant damage. Where natural enemies are excluded or with excessively high nitrogen levels, outbreaks of green peach aphid (Mysus persicae) can occur. High numbers of aphids cause leaves to curl. Insecticidal soap used at weekly intervals can reduce infestations. Normally, beneficial insects keep aphid populations below damaging levels.
Because water spinach is not nationally recognized as a legal food crop there are no pesticides specifically labeled for it. It is important not to use pesticides that are not labeled for the crop.
Two critical reasons for this are:
1. It is illegal
2. There is a risk that illegal or toxic residues will remain on the crop and harm those who eat it.
However, it would be legal to use pesticides that are labeled for the entire leafy vegetable crop group. The specific target pest does not have to be listed on the label but the leafy greens crop group must be on the label. Pay special attention to label restrictions regarding the days to harvest interval. In Massachusetts, there are general use insecticide products with the following active ingredients that are labeled for use on leafy vegetables; spinosad, neem, Beauvaria bassiana, and permethrin (dilute products with 0.25% active ingredient; please note that some permethrin products are restricted or do not have the leafy green crop group on the label).
Water spinach requires rapid and careful post-harvest handling to maintain quality. Once harvested, shoot tips and leaves easily wilt. Cool in 50°F as soon as possible after harvest, and maintain high relative humidity with
good ventilation. Produce should be used soon after harvest to minimize quality loss.

 

Ipomoea aquatica is a semi-aquatic tropical plant grown as a leaf vegetable. Its precise natural distribution is unknown due to extensive cultivation, with the species found throughout the tropical and subtropical regions of the world.

Common names include water spinach, swamp cabbage, water convolvulus, water morning-glory, kangkung (Malay), kang kung (Sinhalese), trawkoon ( Khmer: ត្រកូន), pak boong (in Thai: ผักบุ้ง) (Thai), rau muống (Vietnamese), kongxincai (Chinese: 空心菜; pinyin: kōngxīncài; literally "hollow vegetable"), or ong choy (Cantonese pronunciation of Chinese: 蕹菜; pinyin: wéngcài).

Ipomoea aquatica grows in water or on moist soil. Its stems are 2-3 m or more long, hollow, allowing them to float, and these root at the nodes. The leaves vary from sagittate (typical) to lanceolate, 5-15 cm long and 2-8 cm broad. The flowers are trumpet-shaped, 3-5 cm diameter, usually white in colour.

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Cultivation and culinary uses

Ong choy water spinach.It is most commonly grown in East and Southeast Asia. Because it flourishes naturally in waterways and does not require much if any care, it is used extensively in Malay and Chinese cuisine, especially in rural or kampung (village) areas. It is not to be mistaken with watercress, which often grows in similar situations.

It has also been introduced to United States of America where its high growth rate caused it to become an environmental problem, especially in Florida and Texas. It has been officially designated by the USDA as a "noxious weed." Despite this ominous lable, the plant is not in any way harmful when consumed ("noxious" is a legal term denoting harmful, in this case, to native plants). In fact, the plant is similar to spinach in its nutritional benefits.

The vegetable is a common ingredient in Southeast Asian dishes. In Singapore, Indonesia and Penang, the leaves are usually stir fried with both Malay and Chinese seasonings, including chile peppers, garlic, ginger, dried shrimp paste (belacan) and other spices. In Penang and Ipoh, it is cooked with cuttlefish and a sweet and spicy sauce. During the Japanese Occupation of Singapore in World War II, the vegetable grew remarkably well and easily in many areas, and become a popular wartime crop.


PenangKangkung BlachanIn Chinese cuisine, there are numerous ways of preparation, but a simple and quick stir-fry either plain or with minced garlic is probably the most common. In Cantonese cuisine, a popular variation adds preserved beancurd - a method known in the Mandarin language as furu. In Hakka cuisine, yellow bean paste is added, sometimes along with fried shallots. The vegetable is also extremely popular in Taiwan, where it grows well.

In Thailand it is frequently stir fried with oyster sauce and shrimp paste. It can be eaten raw with Lao green papaya salad.

In Vietnam, it once served as a staple vegetable of the poor (known as 'rau muống'). In the south, it is cut into thin pieces and eaten with many kinds of noodles, and used as a garnish as well. Through the course of time, Ipomoea aquatica has developed into being ingredient for many daily vegetable dishes of Vietnamese cuisine as a whole.

In the Philippines, it is usually sauteed in cooking oil, onions, garlic, vinegar, and soy sauce. This dish is called "adobong kangkong". It is also a common leaf vegetable in sour fish and meat stews like "sinigang".

 

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