6.
Betula papyrifera
Marshall, Arbust. Amer. 19. 1785.
Paper birch, canoe birch, white birch, bouleau blanc, bouleau à papier
Betula alba
Linnaeus var.
papyrifera
(Marshall) Spach;
B
.
papyracea
Aiton;
B
.
papyrifera
var.
commutata
(Regel) Fernald;
B
.
papyrifera
var.
elobata
(Fernald) Sargent;
B
.
papyrifera
var.
macrostachya
Fernald;
B
.
papyrifera
var.
pensilis
Fernald;
B
.
papyrifera
var.
subcordata
(Rydberg ex B. T. Butler) Sargent
Trees , to 30 m, usually 20 m or shorter; trunks often single, sometimes 2 or more, mature crowns narrowly round. Bark of young trunks and branches dark reddish brown, smooth, in maturity creamy to chalky white or pale to (infrequently) dark brown, readily exfoliating in paper-thin sheets; lenticels pale, horizontal, in maturity dark, much expanded, horizontal. Twigs without strong odor and taste of wintergreen, slightly to moderately pubescent, infrequently with scattered, small, resinous glands. Leaf blade ovate with 9 or fewer pairs of lateral veins, 5--9(--12) × 4--7 cm, base rounded, cuneate, or truncate, margins sharply to coarsely or irregularly doubly serrate or serrate-dentate, apex acute to short-acuminate; surfaces abaxially sparsely to moderately pubescent, often velutinous along major veins and in vein axils, covered with minute, resinous glands. Infructescences pendulous, cylindric, 2.5--5 × 0.6--1.2 cm, readily shattering with fruits in late fall; scales pubescent to glabrous, lobes diverging at or proximal to middle, central lobe narrowly elongate, obtuse, lateral lobes about equal in length to central lobe but several times broader, strongly divergent, held nearly at right angles to axis. Samaras with wings as broad as or slightly broader than body, extended nearly beyond body apically. 2 n = 56, 70, 84.
Flowering late spring. Moist, ± open, upland forest, especially on rocky slopes, also sometimes in swampy woods; 300--900 m; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Colo., Conn., Idaho, Ill., Ind., Iowa, Maine, Mass., Mich., Minn., Mont., Nebr., N.H., N.J., N.Y., N.Dak., Oreg., Pa., R.I., S.Dak., Vt., Va., Wash., Wis., Wyo.
Betula papyrifera
is a well-known tree of the northern forest with its paper-thin, white, peeling bark. The bark, which has a high oil content and is consequently waterproof, was used for a wide variety of building and clothing purposes by the American Indians, including the covering of the familiar birch bark canoe. It is still used for various purposes, including basketmaking, in Canada and Alaska. Variants having more or less close, dark brown bark (
B. papyrifera
var.
commutata
) occur locally throughout the wide range of this species; this characteristic appears to be largely environmentally caused. The species is an important successional tree, coming up readily after fires, logging, or the abandonment of cultivated land. The relatively soft, whitish wood is used extensively for such items as clothespins, spools, ice cream sticks, and toothpicks, as well as for pulpwood for paper.
Betula papyrifera
is the state tree of New Hampshire.
Native Americans use
Betula papyrifera
medicinally in enemas, to shrivel the womb, to alleviate stomach cramps and pain, and as a tonic (D. E. Moerman 1986).
Betula
×
sandbergii
Britton is a fairly common hybrid, occurring where the ranges of the parents (
B. papyrifera
Marshall and
B. pumila
Linnaeus) come into contact. In most vegetative features it is intermediate between the parental conditions (K. E. Clausen 1963; C. O. Rosendahl 1928).
