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Chestnut Oak Quercus prinus (Quercus montana)


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Chestnut Oak, bark
credit: Mwanner/CCSA

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Family: Fagaceae, Beech view all from this family

Description Quercus prinus (syn. Quercus montana), this member of the white oak group (Quercus sect. Quercus) is native to the eastern United States. It is one of the most important ridgetop trees from southern Maine southwest to central Mississippi, with an outlying northwestern population in southern Michigan. It is also sometimes called "rock oak" because of montane and other rocky habitats. As a consequence of its dry habitat and ridgetop exposure, it is not usually a large tree, typically 18-22m (60-70 ft) tall; occasional specimens growing in better conditions can however become large, with trees up to 40-43 m (130-140 ft) tall known. They tend to have a similar spread of 18-22m (60-70 ft). A 10-year-old sapling will stand about 5 m (16 ft) tall.

Extensive confusion between the chestnut oak (Quercus prinus) and the swamp chestnut oak (Quercus michauxii) has occurred, and some botanists have considered them to be the same species in the past. The name Quercus prinus was long used by many botanists and foresters for both.

The chestnut oak is readily identified by its massively-ridged dark gray-brown bark, the thickest of any eastern North American oak. The leaves are 12-20 cm long and 6-10 cm broad, shallowly lobed with 10-15 rounded lobes on each margin; they are virtually identical to the leaves of swamp chestnut oak and chinkapin oak, but the trees can readily be distinguished by the bark, that of the chinkapin oak being a light ash-gray and somewhat peeling like that of the white oak and that of swamp chestnut oak being paler ash-gray and scaly. The chinkapin oak also has much smaller acorns than the chestnut oak. The chestnut oak is easily distinguished from the swamp white oak because that tree has whitened undersides on the leaves. Another important distinction between the chestnut oak and the swamp chestnut oak is by the habitat; if it grows on a ridge, it is chestnut oak, and if it grows in wet bottomlands, it is probably the more massive swamp chestnut oak; however, this is not fully reliable.

Characteristics of the chestnut oak include:
Bark: Dark, fissured into broad ridges, scaly. Branchlets stout, at first bronze green, later they become reddish brown, finally dark gray or brown. Heavily charged with tannic acid.
Wood: Dark brown, sapwood lighter; heavy, hard, strong, tough, close-grained, durable in contact with the soil. Used for fencing, fuel, and railway ties. Sp. gr., 0.7499; weight of cu. ft., 46.73 lbs.
Winter buds: Light chestnut brown, ovate, acute, one-fourth to one-half of an inch long.
Leaves: Alternate, five to nine inches long, three to four and a half wide, obovate to oblong-lanceolate, wedge-shaped or rounded at base, coarsely crenately toothed, teeth rounded or acute, apex rounded or acute. They come out of the bud convolute, yellow green or bronze, shining above, very pubescent below. When full grown are thick, firm, dark yellow green, somewhat shining above, pale green and pubescent below; midribs stout, yellow, primary veins conspicuous. In autumn they turn a dull yellow soon changing to a yellow brown. Petioles stout or slender, short. Stipules linear to lanceolate, caducous.
Flowers: May, when leaves are one-third grown. Staminate flowers are borne in hairy aments two to three inches long; calyx pale yellow, hairy, deeply seven to nine-lobed; stamens seven to nine; anthers bright yellow. Pistillate flowers on short spikes; peduncles green, stout, hairy; involucral scales hairy; stigmas short, bright red.
Acorns: Annual, singly or in pairs; nut oval, rounded or acute at apex, bright chestnut brown, shining, one and a quarter to one and one-half inches in length; cup, cup-shaped or turbinate, usually inclosing one-half or one-third of the nut, thin, light brown and downy within, reddish brown and rough outside, tuberculate near the base. Scales small, much crowded toward the rim sometimes making a fringe. Kernel white, sweetish.

The acorns of the chestnut oak are among the largest of native American oaks, surpassed in size only by the bur oak and possibly swamp chestnut oak.

This species is a predominant ridge-top tree in eastern North American hardwood forests. It often grows with multiple trunks, often as a result of prior injury to the main stem. It is a long-lived tree, with high-quality timber when well-formed.

Habitat Mountains.

Range New England, Mid-Atlantic, Great Lakes, Southeast.