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.)
