A shrub or small tree to about 25 ft. Leaves 11⁄2 to 4 in. long, oval or ovate, rounded or pointed at the apex, broadly obtuse or rounded at the base, sharply and unevenly double-toothed, glabrous above, downy or glabrous and pale green beneath. Male catkins up to 4 in. long, appearing before the leaves. Female catkins upright, 2⁄5 to 3⁄5 in. long.
Native of N. America from Newfoundland to British Columbia, also ranging southward on the eastern side of the continent to W. Virginia, Ohio, and Minnesota. It is a hardy shrub of no particular merit, but useful in cold, wet situations. Its close relationship to A. incana, the grey alder of the Old World, is most evident in the following variety:
var. americana (Reg.) Fern. A. incana americana Reg.; A. incana var. glauca Loud., not Ait. – Leaves glaucous beneath.
A. serrulata (Ait.) Willd. Betula serrulata Ait. – A closely allied species, differing chiefly in its leaves, which are usually broadest above the middle and have the margins set with fine, nearly regular teeth. It is confined to the eastern and north-central United States.