E-Flora BC: Electronic Atlas of the Flora of British Columbia

Betula nana subsp. exillis L.
scrub birch
Betulaceae (Birch family)

Introduction to Vascular Plants

© Gerry & Wendy Ansell  Email the photographer   (Photo ID #70848)

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Distribution of Betula nana ssp. exillis
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This species occurs in North America in Greenland, Canada and the US where it is found in in Arctic and alpine tundra, acidic rocky slopes and barrens, muskegs, peat bogs, stream banks, open subalpine summits (Furlow, 2012).

Flora North America online (Furlow 2012) provides the following species description:

"Shrubs, spreading or ascending, to 3 m. Bark dark brown, smooth, close; lenticels pale, inconspicuous, unexpanded. Twigs without taste or odor of wintergreen, essentially glabrous to sparsely pubescent, usually conspicuously covered with large, warty, resinous glands. Leaf blade mostly obovate to nearly orbiculate with 2--6 pairs of lateral veins, 0.5--3 × 1--2.5 cm, base cuneate to rounded, margins dentate-crenate, teeth obtuse to rounded, apex obtuse to rounded; surfaces abaxially glabrous to moderately pubescent, especially along major veins and in vein axils, often covered with resinous glands. Infructescences erect, cylindric, 1--2.5 × 0.5--1.2 cm, shattering with fruits in fall; scales glabrous, lobes diverging distal to middle, central lobe elongate, lateral lobes ascending, somewhat shorter and broader than central lobe. Samaras with wings narrower than body, broadest near summit, extended slightly beyond body apically. 2 n = 28."

Because of hybridization with B. pumila and B. nana, this species is a "confusing complex of intermediate forms" (Furlow 2012).

Species Information

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Deciduous shrub, 0.3-2 m tall; young twigs densely glandular and distinctly short-hairy.
Alternate, deciduous, oval to round, usually coarsely toothed, thick and leathery in texture, 0.5-3 cm long; leaf stalks less than 1 cm long.
Male and female flowers in separate catkins 1-2.5 cm long; flowers emerging before or with the leaves; catkins breaking up at maturity.
Nutlets with wings relatively narrow, less than half the width of the body of the nutlets.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Wet to moist bogs, fens, streamsides, marshes, meadows and rocky slopes from the montane to the alpine zones; common throughout BC east of the Coast-Cascade Mountains; N to AK, YT and NT, E to NB and NS, and S to MN, CO and N CA.

Source: The Illustrated Flora of British Columbia

Taxonomic and Nomenclatural Links

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