Betula pendula
Betula neoalaskana
bouleau pleureur, European birch, European weeping birch, European white birch, silver birch, weeping birch
Alaska birch, Alaska paper birch, northwestern white birch, paper birch, resin birch
of mature trunks and branches creamy to silvery white, smooth, exfoliating as long strands;
lenticels dark, horizontally expanded.
of young trunks and branches reddish brown, when mature becoming pinkish white to light red (starkly white in interior Alaska;
D.
pendulous;
twigs glabrous, usually dotted with small resinous glands.
glabrous, covered with conspicuous resinous glands.
blade broadly ovate to rhombic with 5–18 pairs of lateral veins, 3–7 × 2.5–5 cm, base cuneate, rarely truncate, margins coarsely and sharply doubly serrate, apex acuminate;
surfaces abaxially glabrous to sparsely pubescent, covered with minute, resinous glands.
blade deltate-ovate with 5–18 pairs of lateral veins, 3–8 × 2–6 cm, base rounded or broadly cuneate, margins coarsely doubly serrate, apex long-acuminate;
surfaces abaxially glabrous to sparsely pubescent, pubescent along major veins and in vein axils, covered with small resinous glands.
erect to nearly pendulous, cylindric, 2–3.5 × 0.6–1 cm, shattering with fruits in fall;
scales adaxially sparsely pubescent, lobes diverging at middle, central lobe obtuse, much shorter than lateral lobes, lateral lobes broad, rounded, extended.
pendulous, cylindric, 2–4 × 0.8–1.2 cm, shattering with fruits in fall;
scales glabrous, margins ciliate, lobes diverging distal to middle, central lobe narrower and equal to or slightly shorter than lateral lobes, lateral lobes broadly angular, extended.
with wings much broader than body, broadest near center, extended beyond body apically.
with wings broader than body, broadest near summit, extended beyond body apically.
.
, pers.
.), smooth, exfoliating in thin sheets.
= 28, 56.
= 28.
Betula pendula
Betula neoalaskana
The Eurasian weeping birch (Betula pendula) is extensively cultivated throughout the temperate range of the flora, and it has been known to persist or to become locally naturalized in several areas, particularly in the Northeast. In vegetative features it resembles B. populifolia Marshall, to which it is closely allied; it can easily be distinguished from the latter by its peeling bark, as well as by its mostly pubescent leaves with somewhat shorter, acuminate apices.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Betula neoalaskana belongs to a circumpolar complex including B. pendula Roth and B. populifolia Marshall (but not B. papyrifera Marshall, with which it has sometimes erroneously been merged). It is most closely related to the Asian members of this group, including B. japonica Siebold, B. mandshurica (Regel) Nakai, and B. platyphylla Sukaczev (T. C. Brayshaw 1976). The species was formerly widely known by the name B. resinifera (Regel) Britton, but that name has been shown to be illegitimate (B. Boivin 1967–1979, 15: 414–418; J. R. Dugle 1969). The name was based on a mixture of Siberian and North American material and has never been lectotypified.
Betula neoalaskana Sargent is known to hybridize with B. papyrifera Marshall, producing B. ×winteri Dugle, and with B. glandulosa, producing B. ×uliginosa Dugle.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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