Bigleaf maple is a large, highly-branched tree reaching 35 m tall. The bark is grey-brown and ridged, and almost always (in western Washington) covered with mosses, lichens, and ferns. The opposite leaves are huge (15-30 cm in diameter), 5-lobed, and smooth margined in the sinuses between lobes. The leaf stalk exudes milky juice when cut. The flowers are greenish-yellow, about 3 mm across, and crowded into pendent cylindrical clusters that appear before or with the leaves. The fruits are double samaras with the two wings held in a V-shape. Bigleaf maple grows abundantly on moist to dry sites, often with Douglas fir, often on sites disturbed by logging or fire, at low to middle elevations.