5c. ssp. saccharum (sugar maple)

A. saccharum f. glaucum (Schmidt) Pax

A. nigrum F. Michx. var. glaucum (Schmidt) Fosberg

Pl. 196 m, n; Map 808

Bark gray to dark gray or brown, somewhat roughened, becoming deeply furrowed and sometimes with peeling ridges on older trees. Leaf blades 6–15 cm long, the undersurface pale green, bluish green, grayish green, or whitish, sometimes glaucous, glabrous or hairy, the lobes tapered to sharply pointed tips, often with secondary lobes or teeth, the sinuses between the main leaf lobes mostly forming angles of less than 90°, the margins sometimes slightly curled under. Calyx frequently hairy, but without dense white hairs on the inner surface that extend past the lobes. Flower stalks elongating to 5–10 cm, usually hairy. Ovary and young fruit glabrous. 2n=26. April–May.

Common throughout Missouri (eastern U.S. west locally to Idaho and Arizona; Canada). Mesic to dry upland forests, margins of glades, ledges and bases of bluffs, and banks of streams, rarely bottomland forests; also moist to dry, shaded, disturbed areas.

As noted above, many of the trees classified as ssp. saccharum in Missouri (particularly those colonizing drier upland forests) possess at least some characteristics of black maples, including leaf blades less strongly divided than the “typical” phase and with hairy undersurfaces. Such trees still have leaves with pale leaf undersurfaces and somewhat shiny upper surfaces, and they also lack the strongly expanded petiole bases of ssp. nigrum. This morphological race is the one most commonly interfering with oak regeneration in drier upland forest sites.