Betula michauxii
Betula nana
bouleau de Michaux, Michaux's birch, Newfoundland dwarf birch
arctic dwarf birch, bog birch, bouleau nain, dwarf birch
without taste and odor of wintergreen, moderately to densely pubescent, not conspicuously resin-coated, without large, warty, resinous glands.
without taste and odor of wintergreen, glabrous to sparsely or moderately pubescent, with or without heavy resinous coating, sometimes covered with warty resinous glands.
blade obovate–reniform, with 2–3 pairs of lateral veins, 0.5–1 × 0.5–1.2 cm, base cuneate, margins deeply crenate-dentate, apex broadly rounded to nearly truncate;
surfaces abaxially usually glabrous.
blade broadly orbiculate or obovate-orbiculate to reniform, with 2–6 pairs of lateral veins, often broader than long, base rounded to nearly cordate, margins deeply crenate, apex rounded;
surfaces abaxially glabrous to sparsely or moderately pubescent.
erect, short-cylindric, 0.5–1 × 0.5–0.8 cm, shattering with fruits in fall;
scales unlobed (lateral lobes sometimes present but greatly reduced), glabrous.
erect, nearly cylindric, shattering with fruits in fall.
with wings not apparent or reduced to narrow ridges.
with wings much narrower than body, broadest near center, not extended beyond body apically.
and pistillate catkins produced season before flowering but retained in buds during winter, expanding along with new growth in spring.
Betula michauxii
Betula nana
This infrequent dwarf birch is distinguished from Betula nana mostly on the basis of its reduced infructescence scales and wetter habitat (J. J. Furlow 1984), characteristics that are also occasionally noted in B. nana. It perhaps might better be treated as a race of that species; in the absence of thorough study of this complex, however, it seems best to follow the traditional treatment (M. L. Fernald 1950c; J. Rousseau and M. Raymond 1950).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Subspecies 3 (2 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Young twigs pubescent, not covered with conspicuous resinous layer; subarctic and arctic ne Canada, s Greenland. | subsp. nana |
1. Young twigs glabrous or only puberulent, covered with thick resinous coating; Alaska, Yukon, n Asia. | subsp. exilis |
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