Betula nana

Linnaeus

Sp. Pl. 2: 983. 1753.

Common names: Arctic dwarf birch bouleau nain
Treatment appears in FNA Volume 3.

Shrubs, sprawling, creeping, or upright, to 1 m. Bark gray to dark-brown, smooth, close; lenticels inconspicuous, unexpanded. Twigs without taste and odor of wintergreen, glabrous to sparsely or moderately pubescent, with or without heavy resinous coating, sometimes covered with warty resinous glands. Leaf-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. Staminate and pistillate catkins produced season before flowering but retained in buds during winter, expanding along with new growth in spring. Infructescences erect, nearly cylindric, shattering with fruits in fall. Samaras with wings much narrower than body, broadest near center, not extended beyond body apically.

Distribution

Alta., B.C., Man., N.W.T., Sask., Yukon, Alaska, Subarctic and arctic of North America, Europe, and Asia

Discussion

Subspecies 3 (2 in the flora).

Selected References

None.

Key

1 Young twigs pubescent, not covered with conspicuous resinous layer; subarctic and arctic ne Canada, s Greenland. Betula nana subsp. nana
1 Young twigs glabrous or only puberulent, covered with thick resinous coating; Alaska, Yukon, n Asia. Betula nana subsp. exilis

"broadest" is not a number. "much narrower" is not a number.

... more about "Betula nana"
rounded +
John J. Furlow +
Linnaeus +
tanniferous +  and furrowed +
gray +  and dark-brown +
exfoliating +
rounded +  and nearly cordate +
2 +  and 3 +
terete +
slender +
solitary +  and in small racemose clusters +
ovoid +  and cylindric +
expanding +
Arctic dwarf birch +  and bouleau nain +
multibracteate +
Alta. +, B.C. +, Man. +, N.W.T. +, Sask. +, Yukon +, Alaska +, Subarctic and arctic of North America +, Europe +  and and Asia +
pistillate +  and staminate +
expanding +
small +  and large +
1 cm10 mm <br />0.01 m <br /> (4 cm40 mm <br />0.04 m <br />) +
membranaceous +
10 cm100 mm <br />0.1 m <br /> (14 cm140 mm <br />0.14 m <br />) +
0.5 cm5 mm <br />0.005 m <br /> (10 cm100 mm <br />0.1 m <br />) +
obovate-orbiculate;reniform +
often broader than long +
inconspicuous +
unexpanded +
not obvious +  and defined +
membranaceous +
2(-3)-carpellate +
1-seeded +  and 2-winged +
not extended +
crowded +  and imbricate +
deciduous +
(1-)3-lobed +
expanding +
not woody +  and leathery +
thicker +  and thin +
2 +  and 3 +
nearly +  and distinct +
abaxially glabrous;sparsely or moderately pubescent +
Betula nana +
species +
excurrent +  and branching +
differentiated +
upright +  and creeping +
much narrower +
tanniferous +
light +, nearly white +  and reddish-brown +
soft +  and hard +