A shrub procumbent at high elevations, rarely more than 4 ft high anywhere; young shoots not downy, but covered with glands. Leaves obovate to roundish- or kidney-shaped, usually 1⁄3 to 3⁄4 in. (sometimes over 1 in.) long, green and glabrous both sides, conspicuously round-toothed; stalks up to 1⁄4 in. long. Fruiting catkins erect, 1⁄2 to 3⁄4 in. long.
Native of N. America, where it reaches across the continent at high latitudes and high altitudes; also of Greenland. It is closely allied to, and can only be confused with, B. nana (q.v.), but is abundantly distinct in its glandular-warted branchlets and longer-stalked leaves. It occupies similar moist positions in nature, and may be planted in similar positions in gardens.
B. glandulifera (Reg.) Butler B. pumila var. glandulifera Reg. – This closely allied species is distinguishable by its hairy, sparingly glandular branchlets. Native mainly of Canada.
From the Supplement (Vol. V)
The taxonomic position of B. glandulifera, mentioned under this species, is controversial. Originally described as a variety of B. pumila, it continues to rank as such in some works, but it has also been included in B. glandulosa without distinction. Both belong to the same group of shrubby birches as B. nana and B. pumila. Also in this group is:
† B. hallii Howell B. glandulosa var. hallii (Howell) Hitchc. – A shrub or a small tree to some 15 ft high, inhabiting boggy situations in western Washington and Oregon. Branchlets clad with a fine velvety indumentum mixed with longer hairs, but with the same wart-like glands seen in B. glandulosa. Leaves mostly elliptic, relatively narrower than in that species.