Betula pumila
Betula kenaica
bog birch, bouleau nain, dwarf birch, glandular birch, low birch, scrub birch, swamp birch
Kenai birch
dark reddish brown, sometimes becoming pinkish or grayish white, smooth, in maturity exfoliating in thin sheets;
lenticels dark, horizontally expanded.
without taste and odor of wintergreen, glabrous to moderately pubescent, with scattered small resinous glands, especially near nodes.
without taste and odor of wintergreen, slightly to moderately pubescent, often with scattered resinous glands.
blade elliptic, obovate, or nearly orbiculate (to sometimes reniform) with 2–6 pairs of lateral veins, 2.5–5(–7) × 1–5 cm, base cuneate to rounded, margins crenate to dentate, apex usually broadly acute or obtuse to rounded;
surfaces abaxially glabrous or slightly pubescent to heavily velutinous or tomentose, often with scattered resinous glands.
blade ovate to nearly deltate with 2–6 pairs of lateral veins, 4–5(–7.5) × 2.5–4.5 cm, base rounded to cuneate, margins coarsely doubly serrate to dentate, teeth relatively sharp, apex acute to short-acuminate;
surfaces abaxially sparsely to moderately pubescent, especially along major veins and in vein axils, often with scattered resinous glands.
erect, cylindric, 0.8–1.5(–2) × 0.8–1 cm, shattering with fruits in fall;
scales glabrous to pubescent, lobes diverging slightly distal to middle, central lobe narrow, elongate, lateral lobes shorter and broader, extended.
erect to nearly pendulous, cylindric, 2–5 × 0.5–1 cm, shattering with fruits in fall;
scales ciliate, lobes diverging at middle, nearly equal in length, strongly divergent.
with wings slightly narrower than body, broadest near center, not extended beyond body apically.
with wings as broad as to somewhat narrower than body, broadest near middle, not extended beyond body apically.
= 56.
= 70.
Betula pumila
Betula kenaica
Betula pumila is sometimes treated (in part) as a variety of B. glandulosa Michaux, to which it is related at a subgeneric or sectional level. On the basis of morphology, however, it forms a cohesive and distinct entity (J. J. Furlow 1984). The two main varieties into which B. pumila is often divided (a more southern B. pumila var. pumila, with mostly pubescent, glandless leaves, and a more northern B. pumila var. glandulifera, with less pubescent, gland-bearing leaves) may represent geographic races; these are not well marked, however, and they do not hold up well when the complex is examined as a whole.
The Ojibwa used Betula pumila medicinally as a gynecological aid and as a respiratory aid (D. E. Moerman 1986).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
The relationship of Betula kenaica to other white-barked birches is not well understood, although it and the following species are evidently closely allied to B. papyrifera, from which they have likely been derived. Betula kenaica differs from B. papyrifera primarily in its smaller stature and in its smaller, blunter-tipped, more coarsely and regularly serrate leaves.
Betula ×hornei Butler (= Betula kenaica W. H. Evans × B. nana Linnaeus), variously intermediate between its parents, is common throughout the range of B. kenaica (which is mostly overlapped by that of B. nana).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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