Flora of North America species comparison

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Betula pendula

Betula occidentalis

bouleau pleureur, European birch, European weeping birch, European white birch, silver birch, weeping birch

black birch, mountain birch, red birch, river birch, water birch
Habit Trees, to 25 m; trunks usually several, crowns spreading. Shrubs, spreading, to 10 m. Bark dark reddish brown to bronze, smooth, close, not readily exfoliating; lenticels pale, horizontally expanded.
Bark

of mature trunks and branches creamy to silvery white, smooth, exfoliating as long strands;

lenticels dark, horizontally expanded.

Branches

pendulous;

twigs glabrous, usually dotted with small resinous glands.

Twigs

without the odor or taste of wintergreen, glabrous to sparsely pubescent, covered with conspicuous, reddish, resinous glands.
Leaf

blade broadly ovate to rhombic with 5–18 pairs of lateral veins, 3–7 × 2.5–5 cm, base cuneate, rarely truncate, margins coarsely and sharply doubly serrate, apex acuminate;

surfaces abaxially glabrous to sparsely pubescent, covered with minute, resinous glands.

blade broadly ovate to rhombic-ovate with 2–6 pairs of lateral veins, 2–5.8 × 1–4.5 cm, base truncate to rounded or cuneate, margins sharply and coarsely serrate or irregularly doubly serrate, teeth mostly long and sharp, basal portion untoothed, apex acute to occasionally short-acuminate;

surfaces abaxially sparsely to moderately pubescent, covered with minute, resinous glands.
Infructescences

erect to nearly pendulous, cylindric, 2–3.5 × 0.6–1 cm, shattering with fruits in fall;

scales adaxially sparsely pubescent, lobes diverging at middle, central lobe obtuse, much shorter than lateral lobes, lateral lobes broad, rounded, extended.

erect to nearly pendulous, cylindric, 2–3(–3.9) × 0.8–1.5 cm, shattering with fruits in fall;

scales glabrous, ciliate, lobes diverging at middle, central lobe narrower and longer than ascending lateral lobes.
Samaras

with wings much broader than body, broadest near center, extended beyond body apically.

with wings broader than body, broadest near summit, extended beyond body apically.
2n

= 28, 56.

= 28.

Betula pendula

Betula occidentalis
Phenology Flowering late spring. Flowering late spring.
Habitat Abandoned plantings, roadsides, edges of bogs, waste places Montane stream banks, slopes, and ridges, also in moist open woods, at edges of marshes, along lakeshores, and in wet swales
Elevation 0–350 m (0–1100 ft) 100–3000 m (300–9800 ft)
Distribution
from FNA
CT; MA; NH; NY; OH; PA; VT; WA; BC; MB; ON; Europe; Asia
[WildflowerSearch map]
[BONAP county map]
from FNA
AK; AZ; CA; CO; ID; MT; ND; NE; NM; NV; OR; SD; UT; WA; WY; AB; BC; MB; NT; ON; SK; YT
[WildflowerSearch map]
[BONAP county map]
Discussion

The Eurasian weeping birch (Betula pendula) is extensively cultivated throughout the temperate range of the flora, and it has been known to persist or to become locally naturalized in several areas, particularly in the Northeast. In vegetative features it resembles B. populifolia Marshall, to which it is closely allied; it can easily be distinguished from the latter by its peeling bark, as well as by its mostly pubescent leaves with somewhat shorter, acuminate apices.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Betula occidentalis is a common, streamside, shrubby birch throughout much of the Rocky Mountains, extending eastward to northwestern Ontario. It has been widely known by the later name B. fontinalis because of questions concerning the legitimacy of Hooker's epithet (J. R. Dugle 1966). Recent changes to the International Code of Botanical Nomenclature (W. Greuter et al. 1994) have clarified the situation, however, and the consensus now is that the earlier name is correct. E. Hultén (1968) believed that the species in Alaska that has been called B. occidentalis consists of an extensive hybrid swarm between B. neoalaskana (as B. resinifera) and B. glandulosa. The studies of J. R. Dugle (1966) do not support a hybrid origin of B. occidentalis in other parts of its range. Additional study will be needed to resolve this problem, both in Alaska and southward.

Betula ×utahensis Britton (= B. occidentalis Hooker × B. papyrifera Marshall) is a common hybrid marked by intermediate characteristics.

Betula papyrifera Marshall var. subcordata (Rydberg) Sargent, formerly recognized in several state, provincial, and regional floras, consists of introgressants of B. occidentalis into B. papyrifera (J. R. Dugle 1966).

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 3. FNA vol. 3.
Parent taxa Betulaceae > subfam. Betuloideae > Betula Betulaceae > subfam. Betuloideae > Betula
Sibling taxa
B. alleghaniensis, B. cordifolia, B. glandulosa, B. kenaica, B. lenta, B. michauxii, B. minor, B. murrayana, B. nana, B. neoalaskana, B. nigra, B. occidentalis, B. papyrifera, B. populifolia, B. pubescens, B. pumila, B. uber
B. alleghaniensis, B. cordifolia, B. glandulosa, B. kenaica, B. lenta, B. michauxii, B. minor, B. murrayana, B. nana, B. neoalaskana, B. nigra, B. papyrifera, B. pendula, B. populifolia, B. pubescens, B. pumila, B. uber
Synonyms B. verrucosa B. fontinalis, B. fontinalis var. inopina, B. microphylla var. fontinalis, B. occidentalis var. fecunda, B. occidentalis var. inopina, B. papyrifera var. occidentalis, B. papyrifera subsp. occidentalis
Name authority Roth: Tent. Fl. Germ. 1: 405. (1788) Hooker: Fl. Bor.-Amer. 2: 155. (1838)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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