Both tree and water chestnuts are delicious, but they are entirely unrelated and belong to two different plant families. Tree chestnuts (Castanea spp.) belong to the beech tree family (Fagaceae), which are forest trees and shrubs. The chestnuts are shiny brown nuts that develop from catkin-like flowers. The water chestnut (Eleocharis dulcis) belongs to the sedge family (Cyperaeae), which are rushlike plants that live in boggy or aquatic places. Water chestnuts are underground stem enlargements called corms or tubers, and the plants have to be dug up to harvest the corms.
Kinds of Tree Chestnuts
Several species of chestnut trees are native to America, Europe, China and Japan. The American chestnut (Castanea dentata) was decimated by a fungus, chestnut blight, which was brought to the United States from Asia in 1900. Within 40 years American chestnuts were almost entirely eliminated. Work is underway to create blight-resistant hybrids with mostly American chestnut ancestry to grow in its native range of U.S. Department of Agriculture plant hardiness zones 5 through 8. Spanish chestnuts (Castanea sativa) are also sensitive to chestnut blight in America, but they grow well in Europe in the equivalent of USDA zones 5 through 7, and they are the source of most edible chestnuts in the United States. Chinese chestnut (Castanea mollissima), hardy in USDA zones 5 through 8, and Japanese chestnut (Castanea crenata), grown in USDA zones 4 through 8, are resistant to the disease, and these two species and resistant hybrids are grown in the United States.
Tree Chestnut Fruits
Tree chestnut fruits have a prickly greenish covering called a burr. Inside are one to three shiny dark brown seeds, which are the chestnuts. The nuts are white inside and vary in sweetness, flavor and size depending on the species. Chinese chestnuts are sweeter and finer textured than Japanese chestnuts, European chestnuts have even sweeter taste and are larger still, and some European cultivars are of gourmet quality. Chestnuts are eaten roasted or otherwise cooked, made into candies or milled into flour. Chestnut trees are tall, with American and Spanish chestnuts attaining over 100 feet in height, and have spreading canopies. They are suited for parks, avenues, estates and woodland gardens. Japanese chestnuts reach 30 to 40 feet and Chinese chestnuts attain 40 feet, both suitable for shade trees or in wildlife gardens.
Widely used in Asian cooking, water chestnuts keep their crunchiness even when well cooked. Tubular, narrow green stems rise to 3 to 5 feet tall, growing in clumps. Water chestnuts grow in USDA zones 10 through 11, needing 220 frost-free days to reach maturity and 4 to 6 inches of standing water while they are growing. Plants are quick-growing and productive, with three to four planted corms yielding 20 to 60 pounds of water chestnuts. Gardeners can grow water chestnuts in large tubs at least 10 inches deep. Containers need a drainage hole and plug.
Water Chestnut Corms
The corms have a brown-colored outside skin and flattened shape similar to that of a chestnut, and the white flesh is sweet and nutty-flavored. At the end of their growing season, drain water from the plants and let the plants dry for a month before digging up the corms. You can sift the corms from the soil and dry them in trays in a shady area. The corms store well in glass jars in the refrigerator, and are eaten raw or cooked.
- Floridata: Castanea Sativa
- University of Florida IFAS Extension: Waterchestnut -- Eleocharis Dulcis (Burm. f.) Trin. ex Henschel
- American Chestnut Cooperators Foundation: Genus Castanea
- University of Florida IFAS Extension: Castanea Mollissima: Chinese Chestnut
- Missouri Botanical Garden: Castanea Crenata
- Forest Ecology and Management: Dominance of Interplanted American Chestnut (Castanea Dentata) in Southwestern Wisconsin, USA
- Exotic Foods: A Kitchen and Garden Guide; Marian Van Atta
- Michael Blann/Photodisc/Getty Images