Often cultivated in the northeastern states as an ornamental tree, growing rapidly in cultivation.
4. [Betula populifolia] Marsh. Gray Birch. White Birch.
Leaves nearly triangular to rhombic, long-pointed, coarsely doubly serrate with stout spreading glandular teeth except at the broad truncate or slightly cordate or cuneate base, thin and firm, dark green and lustrous and somewhat roughened on the upper surface early in the season by small pale glands in the axils of the conspicuous reticulate veinlets, 2½′—3′ long, 1½′—2½′ wide, with a stout yellow midrib covered with minute glands, and raised and rounded on the upper side, and obscure yellow primary veins; turning pale yellow in the autumn; petioles slender, terete, covered with black glands, often stained with red on the upper side, ¾′—1′ long; stipules broadly ovate, acute, membranaceous, light green slightly tinged with red. Flowers: staminate aments usually solitary or rarely in pairs, 1¼′—1½′ long, about ⅛′ thick during the winter, becoming 2½′—4′ long, with ovate acute apiculate scales; pistillate aments slender, as long as their glandular peduncles about ½′ in length, with ovate acute pale green glandular scales. Fruit: strobiles cylindric, pubescent, obtuse at apex, about ¾′ long and ⅓′ thick, pendant or spreading on slender stems; nut ellipsoidal to obovoid, acute or rounded at base, a little narrower than its obovate wing.
A short-lived tree, 20°—30° or exceptionally 40° high, with a trunk rarely 18′ in diameter, short slender often pendulous more or less contorted branches usually clothing the stem to the ground and forming a narrow pyramidal head, and branchlets roughened by small raised lenticels, resinous-glandular when they first appear, gradually growing darker, bright yellow and lustrous before autumn like the young stems, bright reddish brown during their first winter, and ultimately white near the trunk; often growing in clusters of spreading stems springing from the stumps of old trees. Winter-buds ovoid, acute, pale chestnut-brown, glabrous, about ¼′ long. Bark about ⅓′ thick, dull chalky white on the outer surface, bright orange on the inner, close and firm, with dark triangular markings at the insertion of the branches, becoming at the base of old trees thicker, nearly black, and irregularly broken by shallow fissures. Wood light, soft, not strong, close-grained, not durable, light brown, with thick nearly white sapwood; used in the manufacture of spools, shoe-pegs and wood pulp, for the hoops of barrels, and largely for fuel.
Distribution. Dry gravelly barren soil or on the margins of swamps and ponds; Prince Edward Island, Nova Scotia, New Brunswick, and the valley of the lower St. Lawrence River southward to northeastern, central and on South Mountain, Franklin County, Pennsylvania, and northern Delaware, and westward through northern New England and New York, ascending sometimes to altitudes of 1800°, to the southern shores of Lake Ontario, and at the foot of Lake Michigan, Indiana; rare and local in the interior, very abundant in the coast region of New England and the middle states; springing up in great numbers on abandoned farm-lands or on lands stripped by fire of their original forest covering; most valuable in its ability to grow rapidly in sterile soil and to afford protection to the seedlings of more valuable and less rapid-growing trees.
A form with deeply divided leaves (var. laciniata Loud.) and one with purple leaves (var. purpurea E & B) are occasionally cultivated.
A shrub believed to be a natural hybrid of B. populifolia with B. pumila Michx. has been found near Mt. Mansfield, Vermont.
5. [Betula cœrulea] Blanch. Blue Birch.
