Trees , often massive, formerly to 30 m, now persisting mostly as multistemmed resprouts to 5-10 m because of widespread destruction by blight. Bark gray, smooth when young, furrowed in age. Twigs glabrous. Leaves: petiole (8-)10-30(-40) mm. Leaf blade narrowly obovate to oblanceolate, 90-300 × 30-100 mm, base cuneate, margins sharply serrate, each tooth triangular, gradually tapering to awn often more than 2 mm, apex acute or acuminate, surfaces abaxially often without stellate trichomes, appearing glabrous but with evenly distributed, minute, multicellular, embedded glands between veins and sparse, straight, simple trichomes concentrated on veins, stellate or tufted trichomes absent. Staminate flowers with conspicuous pistillodes, whitish or yellowish straight hairs in center of flower. Pistillate flowers 3 per cupule. Fruits: cupule 4-valved, enclosing 3 flowers/fruits, valves irregularly dehiscing along 4 sutures at maturity, spines of cupule essentially glabrous, with a few scattered simple trichomes; nuts 3 per cupule, obovate, 18-25 × 18-25 mm, flattened on 1 or both sides, beak to 8mm excluding styles. Flowering summer (Jun-Jul). Previously common in rich deciduous and mixed forests, particularly with oak; 0-1200 m; Ont.; Ala., Conn., Del., Fla., Ga., Ill., Ind., Ky., La., Maine, Md., Mass., Mich., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Vt., Va., W.Va., Wis. The American chestnut was one of the most important dominant forest trees of eastern North America prior to 1930. The nuts, sweet and edible, were a favorite confection in the eastern United States. The wood is light, strong, and resistant to decay; it was widely used for construction, furniture, and decorative trim. The bark was used for tanning leather. Native Americans used various parts of the plants of Castanea dentata medicinally as a cough syrup and to treat whooping cough, for heart trouble, and as a powder for chafed skin (D. E. Moerman 1986).

After 1930, most populations of Castanea dentata were nearly destroyed by the chestnut blight, caused by the introduced fungus Cryphonectria parasitica (Murrill) M. E. Barr [= Endothia parasitica (Murrill) P. J. Anderson & H. W. Anderson]. While chestnuts persist in many localities, the plants are mostly resprouts that rarely, if ever, produce viable seed.

Virtually all known natural populations remain infected with the blight, and various studies continue in an effort to find ways to improve growth and vitality of infected trees. The species was widely planted outside of its native range (e.g., Illinois, Indiana, Iowa, Michigan, and Wisconsin), and some of these plantings remain blight-free because of their isolation. One particularly large grove was planted near West Salem, Wisconsin, in 1880, and continuing regeneration through seedlings has been documented (F. L. Paillet and P. A. Rutter 1989). Unfortunately, chestnut blight has recently been discovered in this isolated population and probably is extending to other isolated plantings in the west.

As part of the effort to introduce blight-resistant strains of the American chestnut, breeding programs have produced hybrids of Castanea dentata in various combinations with exotic species of chestnut. These hybrids are often extremely difficult to identify because they may derive from as many as three parents in complicated backcrosses. When identifying trees suspected of being introduced, one should be aware of the three most commonly cultivated exotic chestnut species, all of which have been collected as sporadic escapes or persistent waifs:

Castanea sativa Miller - Spanish chestnut

Leaf blade abaxially with sparse to dense covering of stellate hairs, also with conspicuous glands as in C . dentata . Petiole relatively long (30 mm or more).

Castanea mollissima Blume - Chinese chestnut

Twigs with spreading hairs. Leaf blade abaxially cobwebby-pubescent, without conspicuous foliar glands found in Castanea dentata . Resistant to blight and widely cultivated in the United States, where it occasionally escapes.

Castanea crenata Siebold & Zuccarini - Japanese chestnut

Leaf blade abaxially with minute, glandular, peltate scales mixed with dense, tangled tomentum. Vegetatively, this species may be di