water chestnut: see sedge.

horse chestnut, common name for some members of the Hippocastanaceae, a family of trees and shrubs of the north temperate zones and of South America. The horse chestnut tree, Aesculus hippocastanum, a native of the Balkan peninsula, is now cultivated in many countries for shade and ornament. Buckeyes are several similar but often smaller North American species of the same genus. Horse chestnuts and buckeyes (as the nuts too are called) somewhat resemble true chestnuts in appearance but are edible only after careful preparation. Some Native Americans ate buckeyes in large quantity after thorough roasting or leaching. Buckeyes, with their eyelike markings, are still carried as charms by some rural people. Ohio is called the Buckeye State from the prevalence of the Ohio buckeye, A. glabra. The wood of the horse chestnut and of the buckeye is soft; it has been used for paper pulp and for carpentry, woodenware, and other similar purposes. A compound derived from the buckeye, aesculin, is a pharmaceutical used as an anti-inflammatory. The only other genus of the family is Billia, evergreens ranging from Colombia to Mexico. Horse chestnuts are classified in the division Magnoliophyta, class Magnoliopsida, order Sapindales, family Hippocastanallae.

chestnut, name for any species of the genus Castanea, deciduous trees of the family Fagaceae (beech or oak family) widely distributed in the Northern Hemisphere. They are characterized by thin-shelled, sweet, edible nuts borne in a bristly bur. The common American chestnut, C. dentata, is native E of the Mississippi but is now nearly extinct because of the chestnut blight, a disease from Asia caused by the fungus Crypthonectria parasitica, and the clear-cutting that resulted when lumber companies anticipated the destruction of chestnut forests by the fungus. The American chestnut was an important source of timber. Efforts are being made to breed a type of American chestnut resistant to the disease, by crossing it with the blight-resistant Chinese and Japanese chestnuts, in order to replace the old chestnut forests. The dead and fallen logs were long the the leading domestic source of tannin. Chestnut wood is porous, but it is very durable in soil and has been popular for fence posts, railway ties, and beams. Edible chestnuts are now mostly imported from Italy, where the Eurasian species (C. sativa) has not been destroyed. The chinquapin belongs to the same genus. Chestnuts are classified in the division Magnoliophyta, class Magnoliopsida, order Fagales, family Fagaceae.

Any of several perennial water plants of the genus Trapa (family Trapaceae), native to Europe, Asia, and Africa, or their edible, nutlike fruit. The water caltrop (T. natans) has two sets of leaves—long, feathery, rootlike, submerged leaves and a loose rosette of floating leaves attached to leafstalks 2–4 in (5–10 cm) long. The small fruit usually has four spiny angles. The Chinese water chestnut (Eleocharis tuberosus or E. dulcis) is a member of the sedge family.

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Family Hippocastanaceae, composed of the buckeyes and the horse chestnuts (genus Aesculus), native to the northern temperate zone. The best-known species of horse chestnut is the common, or European, horse chestnut (A. hippocastanum), native to southeastern Europe but widely cultivated as a large shade and street tree. The Champs-Élysées in Paris is lined with rows of horse-chestnut trees.

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Plant disease caused by the fungus Endothia parasitica. Accidentally imported from East Asia and first observed in 1904 in New York, it has killed almost all native American chestnuts (Castanea dentata) in the U.S. and Canada and is destructive in other countries. Other blight-susceptible species include the European chestnut (C. sativa), the post oak (Quercus stellata), and the live oak. Symptoms include reddish brown bark patches that develop into sunken or swollen and cracked cankers that kill twigs and limbs. Leaves on such branches turn brown and wither but remain attached for months. Gradually the entire tree dies. The fungus persists for years in short-lived sprouts from old chestnut roots and in less susceptible hosts. It is spread locally by splashing rain, wind, and insects, and over long distances by birds. Chinese (C. mollissima) and Japanese (C. crenata) chestnuts are resistant.

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Any of four species of deciduous ornamental and timber trees of the genus Castanea, in the beech family. Native to temperate regions of the Northern Hemisphere, they bear burrlike fruits that contain two or three edible nuts. The usually tall trees have furrowed bark and lance-shaped leaves. The American chestnut (C. dentata), which once extended over a large area of eastern North America, has been almost eliminated by chestnut blight. The other three species are the European chestnut (C. sativa), the Chinese chestnut (C. mollissima), and the Japanese chestnut (C. crenata). The nuts of these three have local importance as food and are exported in large quantities, and varieties of all three are cultivated as ornamentals. The European chestnut produces useful timber as well; the American chestnut also was an important source of lumber and nuts before the arrival of the blight.

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