Bog Birch

Betula pumila is sometimes treated (in part) as a variety of B . glandulosa Michaux, to which it is related at a subgeneric or sectional level. On the basis of morphology, however, it forms a cohesive and distinct entity (J. J. Furlow 1984). The two main varieties into which B . pumila is often divided (a more southern B . pumila var. pumila , with mostly pubescent, glandless leaves, and a more northern B . pumila var. glandulifera , with less pubescent, gland-bearing leaves) may represent geographic races; these are not well marked, however, and they do not hold up well when the complex is examined as a whole.

The Ojibwa used Betula pumila medicinally as a gynecological aid and as a respiratory aid (D. E. Moerman 1986).

Shrubs , coarse, irregular, or spreading, to 4 m. Bark dark reddish brown, smooth, close; lenticels pale, inconspicuous. Twigs without taste and odor of wintergreen, glabrous to moderately pubescent, with scattered small resinous glands, especially near nodes. Leaf blade elliptic, obovate, or nearly orbiculate (to sometimes reniform) with 2--6 pairs of lateral veins, 2.5--5(--7) × 1--5 cm, base cuneate to rounded, margins crenate to dentate, apex usually broadly acute or obtuse to rounded; surfaces abaxially glabrous or slightly pubescent to heavily velutinous or tomentose, often with scattered resinous glands. Infructescences erect, cylindric, 0.8--1.5(--2) × 0.8--1 cm, shattering with fruits in fall; scales glabrous to pubescent, lobes diverging slightly distal to middle, central lobe narrow, elongate, lateral lobes shorter and broader, extended. Samaras with wings slightly narrower than body, broadest near center, not extended beyond body apically. 2 n = 56.

St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Calif., Colo., Conn., Idaho, Ill., Ind., Iowa, Kans., Maine, Mass., Mich., Minn., Mont., Nebr., N.J., N.Y., N.Dak., Ohio, Oreg., Pa., S.Dak., Vt., Wash., Wis., Wyo.

Flowering late spring.

Bogs, calcareous fens, wooded swamps, muskegs, lake shores; 0--700m.

Betula borealis Spach; B. glandulifera (Regel) B. T. Butler; B. glandulosa Michaux var. glandulifera (Regel) Gleason; B. glandulosa var. hallii (Howell) C. L. Hitchcock; B. hallii Howell; B. nana Linnaeus var. glandulifera (Regel) B. Boivin; B. pubescens Ehrhart subsp. borealis (Spach) A. Löve & D. Löve; B. pumila Linnaeus var. glabra Regel; B. pumila var. glandulifera Regel; B. pumila var. renifolia Fernald

Betula pumila (dwarf birch or bog birch) is a deciduous shrub native to North America. Bog birch occurs over a vast area of northern North America, from Yukon in the west to New England in the east and all the way to Washington and Oregon, inhabiting swamps and riparian zones in the boreal forests.