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A deciduous tree, occasionally 30 to 40 ft high, usually much less; branchlets reddish and glabrosus. Leaves three-lobed (or five-lobed with the basal pair of lobes much reduced), 2 to 4 in. across, heart-shaped at the base; lobes triangular or oblong, entire or with three secondary lobes; downy beneath, especially along the ribs; stalks reddish, glabrous. Flowers yellow, borne in drooping short-stalked clusters, appearing with the leaves. Fruit glabrous; keys 1 to 11⁄4 in. long; wings 1⁄4 to 1⁄2 in. wide, diverging at about 60°.
Native of western N. America; originally discovered by Thos. Nuttall on the head-waters of the Columbia River in N. Montana, whence it extends southward to Arizona and New Mexico. It is represented in the Kew collection by plants received from Prof. Sargent in 1885, which was probably its first introduction to England. It is allied to the sugar maple (A. saccharum), and is treated as a subspecies of it by Murray (Morris Arb. Bull., Vol. 18, p. 45, 1967). It represents that species on the western side of N. America.