Betula pubescens subsp. tortuosa
Consp. Fl. Eur., 672. 1881
Shrubs, 1–12 m; trunks usually many, often interlacing, branches ascending. Twigs with numerous small resinous glands. Leaf blade ovate, rhombic-ovate, or suborbiculate-rhombic, 1–2.5(–3.5) × 1–2(–3) cm, base cuneate to truncate, margins coarsely serrate or dentate, apex acute; surfaces abaxially moderately pubescent. Infructescences 1–1.5(–2) × 0.4–0.8 cm; scales pubescent to glabrous, often ciliate, central lobe oblong or narrowly triangular, apex acute to obtuse, lateral lobes divergent and ascending, about equal in length but somewhat broader. Samaras with wings about equal in diameter to body, broadest near summit, usually extended beyond body apically. 2n = 56.
Phenology: Flowering late spring.
Habitat: Protected inland valleys
Elevation: 0–200 m
Native, Greenland, Europe.
Betula pubescens subsp. tortuosa, which also occurs in Iceland, the mountains of Scandinavia, and arctic Europe, is native to southwestern Greenland; it has also been reported as well from Baffin Island, although I have not seen specimens. Based on pollen analyses (B. Fredskild 1991), this subspecies arrived in Greenland from Europe ca. 3500 years ago. Hybridization of this taxon with other birches in Greenland, Iceland, and Scandinavia has been studied by M. Sulkinoja (1990).