Flower:

Male and female flowers are borne separately on the same tree (monoecious), in clusters called catkins. Male catkins are in groups of 1 to 3 at tips of 1 year old twigs, pendulous in flower, 2¼ to 4½ inches long, developing in fall as a slender spike of tightly appressed scales and opening up the following spring. Female catkins are erect and stout, cylindrical, ¾ to 1½ inches long from new, spur-like lateral twigs on the same branch as the males.

Leaves and bark:

Leaves are alternate and simple in pairs on short, spur-like lateral twigs, and singly on the new, elongating terminal branchlets. The blade is lance-elliptic to egg-shaped, 2 to 4¼ inches long, 1¼ to 2½ inches wide, pointed at the tip, the base rounded to somewhat heart-shaped, on a ¼ to 2/3 inch hairy stalk. Edges are double-toothed, upper surface dark green and sparsely hairy becoming smooth, lower surface lighter green with hairs on veins and with tufts in vein axils.

Twigs are greenish brown to reddish or purplish brown with scattered lenticels (pores), new growth hairy becoming mostly hairless and shiny the second year. Twigs have a wintergreen odor when broken, with a wintergreen flavor as well.

Bark on younger stems and branches is bronze or yellowish brown, shiny with large, rough horizontal lenticels, older bark peeling in thin, curly strips, basal trunk bark reddish brown, breaking up into coarse, shaggy plates. Trunks can get up to 36 (48) inches dbh.

Fruit:

Female catkins become erect, oval to egg-shaped, cone-like clusters, ¾ to 1 inch long, of winged nutlets each around 1/8 inch long, green drying to brown.

Notes:

While Yellow Birch is fairly common to much of Minnesota's eastern hardwood forests and can attain both great age and size, it is surprisingly unfamiliar to many Minnesotans who may readily recognize it as a birch - but which one? While Paper Birch (Betula papyrifera) may be somewhat reddish colored on younger branches, its older bark is distinctly white and typically chalky textured. The bark on Heart-leaved Birch (B. cordifolia) is also consistently whiter and its leaves are heart-shaped at the base. River Birch (B. nigra), which is only found in floodplain forests of the lower Mississippi, does have coarse, platy bark on its lower trunk like Yellow Birch, but its younger stems have have very loose, large papery sheets, often reddish brown and chalky textured. The yellowish brown to bronze bark on younger yellow birch branches is distinctively shiny and, when shedding, the strips are very narrow and papery thin. The wintergreen odor and taste of young broken twigs is also unique from all other Minnesota birches, though Sweet Birch (B. lenta), an eastern species not found in Minnesota, shares this trait. In spite of its fairly broad site tolerance and geographic range in Minnesota, it is rarely if ever used or seen in urban landscape plantings.