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FNA | Family List | FNA Vol. 3 | Betulaceae | Betula

9. Betula pubescens Ehrhart, Beitr. Naturk. 5: 160. 1790.

Betula alba var. pubescens (Ehrhart) Spach

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.

Subspecies 3 (2 in the flora): Greenland; introduced elsewhere in North America; Iceland; Eurasia.

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.)

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.   9a subsp. pubescens
+ Leaf blade 1–2.5(–3.5) cm; twigs ± glandular; wing of samara about as wide as body; native shrubs of sw Greenland.   9b subsp. tortuosa

Lower Taxa


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