Trees and shrubs, to 25 m; crowns open. Bark light to dark gray, reddish, or brown, smooth, or in age broken into irregular plates; lenticels present or absent, conspicuous, enlarged or unexpanded. Winter buds stipitate, ellipsoid, 4–7 mm, apex rounded to nearly acute; stalk 1–3 mm; scales 2–3, equal, valvate, resin-coated. Leaf blade narrowly ovate to elliptic, base cuneate to narrowly rounded, margins doubly serrate, with distinctly larger secondary teeth, apex acute or short-acuminate to obtuse. Inflorescences formed season before flowering and exposed during winter. Flowering before new growth in spring. Infructescences ovoid to nearly cylindric; peduncles relatively short and stout. Samaras elliptic to obovate, wings narrower than body, irregular in shape.
Alta., B.C., Man., N.B., N.S., N.W.T., Nfld. and Labr. (Nfld.), Ont., P.E.I., Que., Sask., Yukon, Alaska, Ariz., Calif., Colo., Conn., Idaho, Ill., Ind., Iowa, Maine, Mass., Md., Mich., Minn., Mont., N.Dak., N.H., N.J., N.Mex., N.Y., Nev., Ohio, Oreg., Pa., R.I., Utah, Va., Vt., W.Va., Wash., Wis., Wyo., Canada
Subspecies 4 (2 in the flora).
Native Americans used Alnus incana medicinally to treat anemia, as an emetic, a compress or wash for sore eyes, and a diaphoretic, for internal bleeding, urinary problems, sprains, bruises or backaches, itches, flux, and piles, to cure saddle gall in horses, and when mixed with powdered bumblebees, as an aid for difficult labor (D. E. Moerman 1986).