Leaves rhombic-lanceolate to ovate, abruptly acuminate, gradually or abruptly narrowed and cuneate or concave-cuneate, or rarely broad and rounded at the mostly entire base, coarsely crenately serrate except near the apex, dark green and lustrous above, dull green below, 2′—4′ long, ¾′—2′ wide, with a slender yellow midrib, thin remote primary veins and obscure reticulate veinlets; petioles slender, nearly terete, 1′—3′ long. Flowers: aments slender, short-stalked, 2′—3′ long, the pistillate becoming 4′ or 5′ long before the fruit ripens; scales scarious, light brown, glabrous, dilated and irregularly divided into filiform lobes; disk of the staminate flower wide, oblique, and membranaceous; stamens numerous, with short filaments and dark red anthers; disk of the pistillate flower deep cup-shaped; ovary broad-ovoid, gradually narrowed above, with large laciniately lobed nearly sessile stigmas. Fruit pedicellate, oblong-ovoid, acute, thin-walled, slightly pitted, about ⅓′ long, 3 or rarely 2-valved; seeds oblong-obovoid, rounded at the apex, light brown, about 1/12′ in length.
A tree, usually about 40° high, with a trunk 12′—18′ in diameter, stout spreading and ascending branches forming a compact round-topped head, and slender terete or slightly 4-angled pale yellow-brown branchlets roughened for two or three years by the elevated oval horizontal leaf-scars. Winter-buds acuminate, resinous, about ⅓′ long, with 6 or 7 light chestnut-brown lustrous scales. Bark on young stems and large branches smooth, nearly white, becoming on old trunks pale gray-brown, about ½′ thick, deeply divided into broad flat ridges.
Distribution. Banks of streams in the arid eastern foothill region of the Rocky Mountains; Assiniboia to the Black Hills of South Dakota, northwestern Nebraska, eastern Wyoming, southern Colorado, and southwestern New Mexico (Fort Bayard, Grant County); in Colorado crossing the Continental Divide to southeastern Utah; passing into the var. Rehderi Sarg. differing in the larger leaves on longer petioles, and in the pubescent branchlets and winter-buds. Borders of streams southeastern New Mexico.
Sometimes planted as a shade-tree in the streets of cities in the Rocky Mountain region.
× Populus Andrewsii Sarg. intermediate in its character between P. acuminata and P. Sargentii and believed to be a natural hybrid of these species has been found growing naturally near Boulder and Walsenburg, Colorado, and as a street tree in Montrose, Colorado.
8. [Populus Fremontii] S. Wats. Cottonwood.
Leaves deltoid or reniform, generally contracted into broad short entire points, or rarely rounded or emarginate at apex, truncate, slightly cordate or abruptly cuneate at the entire base, coarsely and irregularly serrate, with few or many incurved gland-tipped teeth, coated like the petioles when they unfold with short spreading caducous pubescence, at maturity thick and firm, glabrous bright green and lustrous, 2′—2½′ long, 2½′—3′ wide, with a thin yellow midrib and 4 or 5 pairs of slender veins; petioles flattened, yellow, 1½′—3′ long. Flowers: staminate aments densely flowered, 1½′—2′ long, nearly ½′ thick, with slender glabrous stems, the pistillate sparsely flowered, with stout glabrous or puberulous stems, becoming before the fruit ripens 4′ or 5′ long; scales light brown, thin and scarious, dilated and irregularly cut at apex into filiform lobes; disk of the staminate flower broad, oblique, slightly thickened on the entire revolute margin; stamens 60 or more, with large dark red anthers; disk of the pistillate flower cup-shaped; ovary ovoid or ovoid-oblong, with 3 or rarely 4 broad irregularly crenately lobed stigmas. Fruit ovoid, acute or obtuse, slightly pitted, thick-walled, 3 or rarely 4-valved, ⅓′—½′ long; pedicel stout, from 1/20′—⅙′ long; seeds ovoid, acute, light brown, nearly ⅛′ in length.
A tree, occasionally 100° high, with a short trunk 5°—6° in diameter, stout spreading branches pendulous at the ends and forming a broad rather open graceful head, and slender terete branchlets light green and glabrous, becoming light yellow before winter, dark or light gray more or less tinged with yellow in their second year, and only slightly roughened by the small 3-lobed leaf-scars. Winter-buds ovoid, acute, with light green lustrous scales, the terminal usually about ⅓′ long and usually two or three times as large as the lateral buds. Bark on young stems light gray-brown, thin, smooth or slightly fissured, becoming on old trees 1½′—2′ thick, dark brown slightly tinged with red, and deeply and irregularly divided into broad connected rounded ridges covered with small closely appressed scales. Wood light brown, with thin nearly white sapwood.