Water Chestnut

Either of two unrelated edible aquatic bulbs, Eleocharis dulcis or Trapa natans, originally from southern China, consumed in Asia since time immemorial. The water chestnut occupies an important place in Chinese, Vietnamese and Japanese cuisine, first used medicinally in China, from which its cultivation spread to India and Madagascar. Today, China is still the major producer of water chestnuts. In North America, we know them from specialty stores, where they're sold canned, most commonly the Eleocharis dulcis variety. The Trapa natans variety is cultivated in some Asian countries and Europe. Both varieties are grown in shallow lakes, swamps and slow-running rivers. Like rice, they need large quantities of water. In Asia, they're often cultivated in rice paddies, where they're planted in spring and harvested the following fall when the rice paddies are drained.

The Eleocharis dulcis variety looks like the regular chestnut, rounded and from 1 to 11⁄2 inches (2.5 to 4 cm) in diameter. The top is slightly flattened and has a little tuft where a green sprout will germinate if the chestnut is not harvested. The bulb is hidden in a rough dark brown skin under which a thin brown skin further protects the white, crispy, juicy, sweet, aromatic flesh. The Trapa has two varieties, T. bicornis, which is ornamented by two curved horns, and T. natans with four horns. They're sometimes called "Jesuit nuts" because they were used for centuries to make rosary beads. These varieties were once extremely popular in Europe, but they're now all but forgotten. The bulbs of these varieties cannot be consumed raw, because they all contain some toxic substances that are neutralized by the cooking process.

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