Betula pubescens subsp. pubescens

Common names: European white birch downy birch
Introduced
Treatment appears in FNA Volume 3.

Trees, narrow, to 20 m; trunk usually 1, branches ascending or spreading. Twigs usually without conspicuous resinous glands. Leaf-blade broadly ovate to rhomic-ovate, 3–4 (–6) × 2–4 (–6) cm, base rounded, truncate, or cuneate, margins finely to coarsely toothed or dentate, apex acute; surfaces abaxially moderately pubescent to velutinous, especially along major veins and in vein-axils. Fruiting catkins 2–3 × 0.8–1.2 cm; scales puberulent and ciliate, lobes diverging at middle, central lobes ovate to delatate, apex acute to obtuse, lateral lobes divergent, about equal in length, several times broader. Samaras with wings somewhat broader than body, broadest near summit, extended beyond body apically. 2n = 56.


Phenology: Flowering late spring.
Habitat: Rocky slopes, scrubs, heaths, and open woods where native, elsewhere in abandoned plantings, moist open roadsides, swales, swampy thickets
Elevation: 0–200 m

Distribution

V3 327-distribution-map.gif

Introduced; B.C., Conn., Ind., Maine, Mass., N.H., Ohio, Pa., Vt., native to Europe

Discussion

Betula pubescens subsp. pubescens is commonly cultivated in northeastern North America, where it has sometimes escaped and persisted, or become adventive but not widely naturalized. It is distinguished from other light-barked species in the East by its relatively small leaves, pubescent twigs, and brownish, mostly unpeeling bark.

Selected References

None.

Lower Taxa

None.

"equal" is not a number."broader" is not a number."broadest" is not a number. "somewhat broader" is not a number.

Acute (?) +  and Obtuse (?) +
John J. Furlow +
Ehrhart +
tanniferous +  and furrowed +
light reddish-brown +  and tan or brownish or grayish white +
exfoliating +
cuneate +, truncate +  and rounded +
2 (?) +  and 3 (?) +
spreading +  and ascending +
slender +
staminate +  and pistillate +
solitary +  and in small racemose clusters +
ovoid +  and cylindric +
expanding +
European white birch +  and downy birch +
multibracteate +
B.C. +, Conn. +, Ind. +, Maine +, Mass. +, N.H. +, Ohio +, Pa. +, Vt. +  and native to Europe +
0–200 m +
pistillate +  and staminate +
expanding +
subpendulous +  and pendulous +
cylindric +
conspicuous +
small +  and large +
Rocky slopes, scrubs, heaths, and open woods where native, elsewhere in abandoned plantings, moist open roadsides, swales, swampy thickets +
1 cm10 mm <br />0.01 m <br /> (4 cm40 mm <br />0.04 m <br />) +
membranaceous +
4 cm40 mm <br />0.04 m <br /> (6 cm60 mm <br />0.06 m <br />) +
4 cm40 mm <br />0.04 m <br /> (6 cm60 mm <br />0.06 m <br />) +
3 cm30 mm <br />0.03 m <br /> (4 cm40 mm <br />0.04 m <br />) +
2 cm20 mm <br />0.02 m <br /> (4 cm40 mm <br />0.04 m <br />) +
dentate +  and toothed +
not obvious +  and defined +
membranaceous +
Flowering late spring. +
2(-3)-carpellate +
Beitr. Naturk. +
1-seeded +  and 2-winged +
extended +
crowded +  and imbricate +
deciduous +
(1-)3-lobed +
expanding +
not woody +  and leathery +
paper-thin +
Introduced +
2 (?) +  and 3 (?) +
nearly +  and distinct +
abaxially moderately pubescent;velutinous +
Betula alba var. pubescens +
Betula pubescens subsp. pubescens +
Betula pubescens +
subspecies +
excurrent +  and branching +
differentiated +
somewhat broader +
tanniferous +
light +, nearly white +  and reddish-brown +
soft +  and hard +