Water chestnut, name of 2 different plants that grow in subarctic and temperate wetlands. The Oriental water chestnut (Eleocharis tuberosa) is in the sedge family and is native to China. Some of its tubelike stems, which may grow to a height of approximately 5 ft (1.5 m), grow upward out of the soil and water. However, some of the stems grow underground and have small, round, edible bulblike swellings at the end called corms. The water caltrop (genus Trapa) also belongs to the water-chestnut family. It is native to tropical and subtropical areas of Africa, Europe, and Asia, and bears edible, nutlike fruits.