Betula pumila
Betula cordifolia
bog birch, bouleau nain, dwarf birch, glandular birch, low birch, scrub birch, swamp birch
bouleau blanc, bouleau à feuilles cordées, heart-leaf paper birch, heartleaf birch, mountain paper birch, mountain white birch
of young trunks and branches dark reddish brown, close, in maturity reddish white to reddish tan or bronze, exfoliating in paper-thin sheets;
lenticels dark, horizontally expanded.
without taste and odor of wintergreen, glabrous to moderately pubescent, with scattered small resinous glands, especially near nodes.
glabrous to sparsely pubescent, often covered with conspicuous, warty, 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 narrowly ovate to ovate with 9–12 pairs of lateral veins, 6–10(–14) × 4–8 cm, base usually cordate, rarely rounded, margins coarsely or irregularly doubly serrate, apex short-acuminate, abaxially sparsely to moderately pubescent, sometimes velutinous or tomentose along major veins and in vein axils, covered with minute, 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.
pendulous or nearly pendulous, cylindric, 2.5–5.5 × 0.6–1 cm, shattering with fruits in fall;
scales glabrous to moderately pubescent, lobes diverging proximal to middle, central lobe elongate, obtuse, lateral lobes ascending, shorter and slightly broader than central lobe.
with wings slightly narrower than body, broadest near center, not extended beyond body apically.
with wings broader than body, broadest near summit, extended beyond body apically.
= 56.
= 28, 56.
Betula pumila
Betula cordifolia
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.)
Betula cordifolia has been reported from Connecticut; I have not seen specimens.
In recent years Betula cordifolia has usually been treated as a variety of B. papyrifera, and perhaps it should be considered an ecological race of that species. It differs from B. papyrifera in polyploid level (diploid and tetraploid in B. cordifolia versus tetraploid, pentaploid, and hexaploid in B. papyrifera) and in vegetative characters, including the number of lateral veins of leaves and the color of bark (W. H. Brittain and W. F. Grant 1967; P. E. DeHond and C. S. Campbell 1989). In the Adirondacks, B. cordifolia and B. papyrifera occur in rather distinct ecological zones (B. cordifolia mostly above 800 m and B. papyrifera generally below this elevation). The species does not appear to occur as far west (Iowa) as stated by M. L. Fernald (1950).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
- Local floras:
BC, 
OR, 
WA - Local Web sites:
CalFlora, CalPhotos, 
Flora NW, 
Go Botany, 
IL Wildflowers, 
KS Wildflowers, 
MI Flora, 
MN Wildflowers, 
PNW Herbaria 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
