Betula pubescens
Beitr. Naturk. 5: 160. 1790.
Trees and shrubs; trunks 1–many. Bark when young dark reddish brown, in maturity light reddish brown to tan or brownish or grayish white, smooth, rather close or readily exfoliating in paper-thin sheets; lenticels pale, horizontal, in maturity dark, horizontally expanded. Twigs without taste and odor of wintergreen, usually covered with short bristly hairs. Leaf blade ovate or rhombic-ovate, margins serrate, apex acute; surfaces abaxially sparsely pubescent to velutinous, especially along major veins and in vein axils, without prominent resinous glands. Fruiting catkins pendulous or subpendulous, cylindric, shattering with fruits in late fall; scales puberulent to glabrous, often ciliate, lobes diverging at middle. Samaras with wings equal to or somewhat broader than body, broadest near summit, extended beyond body apically.
Distribution
B.C., Conn., Ind., Maine, Mass., N.H., Ohio, Pa., Vt., Greenland, introduced elsewhere in North America, Iceland, Eurasia.
Discussion
Subspecies 3 (2 in the flora).
Betula pubescens was used medicinally by the Cree for chafed skin, and by the Ojibwa as a seasoner in medicines and a component in a maple syrup mixture used to relieve stomach cramps (D. E. Moerman 1986, as B. alba).
Betula alba Linnaeus is a long-standing nomen ambiguum that had not been in use (until recently) because it included two taxa whose names had been widely adopted long ago. At this time a proposal to reject Betula alba is in press, and possibly a decision will be made before the end of the year (R. Brummitt, pers. comm.; Fred Barrie, pers. comm.)
Selected References
None.
Key
| 1 | Leaf blade 3–4(–6) cm; twigs usually without conspicuous resinous glands; wing of samara 1–1.5 times as wide as body; trees usually with single trunk, persisting or escaped from cultivation. | Betula pubescens subsp. pubescens |
| 1 | Leaf blade 1–2.5(–3.5) cm; twigs ± glandular; wing of samara about as wide as body; native shrubs of sw Greenland. | Betula pubescens subsp. tortuosa |