Paper Birch

The relationship of Betula kenaica to other white-barked birches is not well understood, although it and the following species are evidently closely allied to B . papyrifera , from which they have likely been derived. Betula kenaica differs from B . papyrifera primarily in its smaller stature and in its smaller, blunter-tipped, more coarsely and regularly serrate leaves.

Betula × hornei Butler (= Betula kenaica W. H. Evans × B . nana Linnaeus), variously intermediate between its parents, is common throughout the range of B . kenaica (which is mostly overlapped by that of B . nana ).

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).

Trees , to 12 m; crowns narrow. Bark dark reddish brown, sometimes becoming pinkish or grayish white, smooth, in maturity exfoliating in thin sheets; lenticels dark, horizontally expanded. Twigs without taste and odor of wintergreen, slightly to moderately pubescent, often with scattered resinous glands. Leaf blade ovate to nearly deltate with 2--6 pairs of lateral veins, 4--5(--7.5) × 2.5--4.5 cm, base rounded to cuneate, margins coarsely doubly serrate to dentate, teeth relatively sharp, apex acute to short-acuminate; surfaces abaxially sparsely to moderately pubescent, especially along major veins and in vein axils, often with scattered resinous glands. Infructescences erect to nearly pendulous, cylindric, 2--5 × 0.5--1 cm, shattering with fruits in fall; scales ciliate, lobes diverging at middle, nearly equal in length, strongly divergent. Samaras with wings as broad as to somewhat narrower than body, broadest near middle, not extended beyond body apically. 2 n = 70.

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.

Yukon; Alaska.

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.

Flowering late spring.

Flowering late spring.

Rocky slopes in the subalpine zone; 0--300m.

Moist, ± open, upland forest, especially on rocky slopes, also sometimes in swampy woods; 300--900m.

Betula kamtschatica (Regel) V. N. Vassiljev var. kenaica (W. H. Evans) C. A. Jansson; B. neoalaskana Sargent var. kenaica (W. H. Evans) B. Boivin; B. papyrifera Marshall var. kenaica (W. H. Evans) A. Henry

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) Sargent