Water spinach floats on hollow stems and feeds half of Asia with almost no effort
Water spinach has hollow stems that let it float, and it roots wherever a node touches mud. It grows along ditches and canals with barely any tending. In Singapore during the Second World War it sprang up so readily that it became a staple crop. Across Asia it goes by dozens of names, kangkung among them.
Botanically it is Ipomoea aquatica, a morning glory relative with arrowhead leaves and white trumpet flowers tinged mauve at the centre. Its stems stretch two to three metres or more. It thrives in the tropics and sulks below about 24 degrees Celsius, and it can be grown from seed or simply from cuttings pushed into wet ground. Hong Kong farmers traditionally raise it either on raised beds between irrigation ditches or directly in flooded fields.
Where it came from is debated. The strongest case points to Southeast Asia, which has the most native names for it, the heaviest use, and local plant diseases adapted to it. A Chinese botanist of the third century described it as a strange southern vegetable brought from abroad, and a claimed ancient Sanskrit name is uncertain. In Africa, the Pacific and northern Australia it has few or no native names, suggesting a late arrival; Indigenous Australians never used it at all.
The kitchen is where it shines. Malaysians, Singaporeans and Indonesians stir-fry the shoots hot and fast with chilli, garlic and fermented shrimp paste. Thais eat it raw beside green papaya salad or cooked in sour curries. Filipinos simmer it in the tangy stew sinigang, sauté it adobo-style with vinegar and soy, or batter and fry the leaves until crisp. Burmese cooks make a salad of blanched stems with lime, fried garlic and toasted rice flour, and southern Chinese kitchens pair it with garlic or fermented tofu. Farmers feed it to cattle, pigs, ducks and fish too.
The same thirst that makes it easy to grow has a downside. The plant soaks up cadmium, lead and mercury from the water, which makes it a candidate for cleaning polluted ponds but a hazard when food crops grow in contaminated or sewage-fed water. It can also pick up parasites carried by pigs in Southeast Asian waterways.
Source: Ipomoea aquatica
