Leaves ovate-lanceolate, gradually narrowed and acuminate at apex, cordate or rounded at base, or narrow-elliptic and acute or acuminate at the ends, finely crenately serrate, with slightly thickened revolute margins, coated when they unfold with the gummy secretions of the bud, glabrous, or puberulous on the under side of the midrib, becoming thin and firm in texture, deep dark green and lustrous above, pale green or glaucous and more or less rusty and conspicuously reticulate-venulose below, 3′—5′ long, 1½′—3′ wide, with thin veins running obliquely almost to the margins; petioles slender, terete, 1½′ long, glabrous or rarely puberulous. Flowers: aments long-stalked, the pistillate becoming 4′—5′ long before the fruit ripens, glabrous or pubescent; scales broadly obovate, light brown and scarious, often irregularly 3-parted at apex, cut into short thread-like brown lobes; disk of the staminate flower oblique, short-stalked; stamens 20—30, with short filaments and large light red anthers; disk of the pistillate flower cup-shaped; ovary ovoid, slightly 2-lobed, with two nearly sessile large oblique dilated crenulate stigmas. Fruit ovoid-oblong, acute and often curved at apex, 2-valved, light brown, about ¼′—⅓′ long, nearly sessile or short-stalked, ½′—⅛′ in length; seeds oblong-obovoid, pointed at apex, narrowed and truncate at base, light brown, about 1/12′ long.
A tree, often 100° high, with a tall trunk 6°—7° in diameter, stout erect branches usually more or less contorted near the end, forming a comparatively narrow open head, and glabrous or occasionally pubescent branchlets marked by oblong bright orange-colored lenticels, much roughened by the thickened leaf-scars, at first red-brown and glabrous or pubescent, becoming bright and lustrous in their first winter, dark orange-colored in their second year, and finally gray tinged with yellow-green; usually much smaller toward the southern limits of its range. Winter-buds saturated with a yellow balsamic sticky exudation, ovoid, terete, long-pointed; terminal 1′ long, ⅓′ broad; axillary about ¾′ long, 1/16′ broad, with 5 oblong pointed concave closely imbricated thick chestnut-brown lustrous scales. Bark light brown tinged with red, smooth or roughened by dark excrescences, becoming on old trunks ¾′—1′ thick, gray tinged with red, and divided into broad rounded ridges covered by small closely appressed scales. Wood light brown, with thick nearly white sapwood.
Distribution. Low often inundated river-bottom lands and swamp borders; Labrador to latitude 65° north in the valley of the Mackenzie River, and to the Alaskan coast, south to northern New England and New York, central Michigan, Minnesota (except in southern and southwestern counties), Turtle Mountains, Rolette County, North Dakota, the Black Hills of South Dakota, northwestern Nebraska (basin of Hat Creek), and in Colorado; the characteristic tree on the streams of the prairie region of British America, attaining its greatest size on the islands and banks of the Peace, Athabasca, and other tributaries of the Mackenzie; common in all the region near the northern boundary of the United States from Maine to the western limits of the Atlantic forests; the largest of the sub-Arctic American trees, and in the far north the most conspicuous feature of vegetation; passing into the variety Michauxii Farwell, with more cordate leaves, slightly pilose on the under side of the midrib and veins; common from Aroostook County, Maine, to the Province of Quebec, Newfoundland, and the shores of Hudson Bay.
Often planted at the north for shelter or ornament.
Populus candicans Ait., the Balm of Gilead of which only the pistillate tree is known, has often been considered a variety of the North American Balsam Poplar. This tree has been long cultivated in the northeastern part of the country and has sometimes escaped from cultivation and formed groves of considerable extent, as on the banks of Cullasagee Creek on the western slope of the Blue Ridge in Macon County, North Carolina. The fact that only one sex is known suggests hybrid origin but of obscure and possibly partly of foreign origin.
5. [Populus trichocarpa] Hook. Black Cottonwood. Balsam Cottonwood.
Leaves broad-ovate, acute or acuminate at apex, rounded or abruptly cuneate at base, finely crenately serrate, glabrous, dark green above, pale and rusty or silvery white and conspicuously reticulate-venulose below, 3′—4′ long, 2′—2½′ wide; petioles slender, pubescent, puberulous, pilose or rarely glabrous, 1½′—2′ in length. Flowers: aments stalked, villose-pubescent, the staminate densely flowered, 1½′—2′ long, ⅓′ thick, the pistillate loosely flowered, 2½′—3′ long, becoming 4′—5′ long before the fruit ripens; scales dilated at the apex, irregularly cut into numerous filiform lobes, glabrous or slightly puberulous on the outer surface; disk of the staminate flower broad, slightly oblique; stamens 40—60, with slender elongated filaments longer than the large light purple anthers; disk of the pistillate flower deep cup-shaped, with irregularly crenate or nearly entire revolute margins; ovary subglobose, coated with thick hoary tomentum, with 3 nearly sessile broadly dilated deeply lobed stigmas. Fruit subglobose, nearly sessile, pubescent, thick-walled, 3-valved; seeds obovoid, apiculate at the gradually narrowed apex, light brown, puberulous toward the ends, 1/12′ long.
A tree, 30°—100° high, with a trunk 1°—3° in diameter, erect branches forming an open head, and slender branchlets terete or slightly angled while young, marked by many orange-colored lenticels, glabrous or when they first appear coated with deciduous rufous or pale pubescence, reddish brown during their first year, gradually becoming dark gray, and roughened by the greatly enlarged and thickened elevated leaf-scars. Winter-buds resinous, fragrant, ovoid, long-pointed, frequently curved above the middle, ¾′ long and ¼′ thick, with 6 or 7 light orange-brown slightly puberulous scales scarious on the margins. Bark ½′—2½′ thick, ashy gray, deeply divided into broad rounded ridges broken on the surface into thick closely appressed scales. Wood light, dull brown, with thin nearly white sapwood.
Distribution. In California in small groves with widely scattered individuals on the coast ranges, the western slope of the Sierra Nevada up to elevations of 6000°—8000°, and on the southern mountains to Mt. Palomar in San Diego County; on the California islands, and on the western slopes of the San Pedro Mártir Mountains, Lower California.