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

bouleau mineur, dwarf birch, dwarf white birch

Habit Trees, to 25 m; trunks usually several, crowns spreading. Shrubs, erect, irregularly spreading, or depressed, to 5 m.
Bark

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

lenticels dark, horizontally expanded.

dark, reddish brown, smooth, close, not readily exfoliating;

lenticels pale, horizontally expanded.

Branches

pendulous;

twigs glabrous, usually dotted with small resinous glands.

Twigs

without odor and taste of wintergreen, glabrous to sparsely pubescent, often dotted with 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 ovate with 2–6 pairs of lateral veins, 1.5–5.5(–8) × 1.5–3(–5) cm, base rounded or cuneate to truncate, margins coarsely doubly serrate, teeth obtuse to rather sharp, toothed nearly to base, apex acute to obtuse;

surfaces abaxially glabrous to moderately pubescent, usually more densely pubescent along major veins, often covered with small 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, cylindric 1–3 × 0.5–1 cm, shattering with fruits in fall;

scales glabrous to moderately pubescent, lobes diverging at middle, central lobe elongate, apex obtuse, lateral lobes ascending, as long as to nearly shorter and broader than central lobe.

Samaras

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

with wings equal to or broader than body, broadest near summit, extending beyond body apically.

2n

= 28, 56.

= 56.

Betula pendula

Betula minor

Phenology Flowering late spring. Flowering late spring.
Habitat Abandoned plantings, roadsides, edges of bogs, waste places Rocky slopes, barrens, and subalpine summits
Elevation 0–350 m (0–1100 ft) 1000–2000 m (3300–6600 ft)
Distribution
from FNA
CT; MA; NH; NY; OH; PA; VT; WA; BC; MB; ON; Europe; Asia
[WildflowerSearch map]
[BONAP county map]
from FNA
ME; NH; NY; NB; NF; NS; ON; QC
[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.)

The origin and relationships of this small birch have not been adequately determined. Betula minor resembles B. pubescens (as B. odorata Bechstein) of Greenland and northern Europe (M. L. Fernald 1950), and it has been combined into that species (A. Löve and D. Löve 1966). Northern and maritime populations of the complex have often been segregated as a separate species (B. borealis Spach sensu M. L. Fernald 1950; B. saxophila of E. Lepage 1976); the name B. minor has been mostly restricted to the subalpine form of northern Appalachian peaks. These two taxa actually constitute a single, somewhat variable, morphologic entity; they are indistinguishable by the minor character differences that have been used to separate them in the past. Because Spach's type of B. borealis consists of material of B. pumila (B. Boivin 1967b), that name must be rejected for this species.

Further complicating matters, E. Lepage (1976) concluded that the type of Betula minor represents a hybrid between individuals of the dwarf species and B. papyrifera, and on that basis, following nomenclatural rules, he renamed the dwarf species B. saxophila, retaining the name B. minor for the hybrid. Leaf shapes and other visible characters of the type fall easily within the limits of variation of B. saxophila, however, and the group is considered here to consist of a single entity, designated by the older name B. minor.

At least in the Adirondacks, Betula minor usually occurs near populations of B. cordifolia and B. glandulosa, and it has frequently been suggested (e.g., E. Hultén 1968; E. Lepage 1976; J. J. Furlow 1990) that it may have originated through hybridization between these species (perhaps followed by polyploidy). The northern populations may similarly consist of a hybrid swarm involving B. papyrifera or B. cordifolia and B. glandulosa. Critical examination of the entire complex, including experimental studies of the patterns of hybridization present, are necessary to unravel its problems satisfactorily.

(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. murrayana, B. nana, B. neoalaskana, B. nigra, B. occidentalis, B. papyrifera, B. pendula, B. populifolia, B. pubescens, B. pumila, B. uber
Synonyms B. verrucosa B. papyracea var. minor, B. pubescens subsp. minor, B. saxophila
Name authority Roth: Tent. Fl. Germ. 1: 405. (1788) (Tuckerman) Fernald: Rhodora 47: 306. (1945)
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