Description

General: Maple Family (Aceraceae): This is a native shrub 1.5-2 m tall or trees 6-10(-12) m tall, variable in form, with short trunk(s) and slender, upright branches, hairless, with slender, reddish-brown shoots and thin; bark smooth, gray or brown. The leaves are deciduous, opposite, 4-12 cm long and wide, sometimes smaller, sometimes divided into three lanceolate leaflets but usually palmately 3(-5)-lobed and veined, the lobes ovate with narrowly acute sinuses and double-toothed edges, with a reddish petiole, shiny dark green above, paler or whitish beneath, turning pale yellow to yellowish-orange or crimson in fall. The flowers are greenish-yellow, with petals usually present, in short, branched terminal or axillary flat-topped clusters 2.5-5 cm long, on drooping stalks. The male and female flowers are usually on separate plants (the species essentially dioecious) or on the same plant (the species technically polygamo-dioecious). The fruits are winged nutlets (samaras) 2.5 cm long, often reddish tinted at maturity, in a long-stalked, wide-spreading pair. The common name is derived from the predominantly Rocky Mountain distribution.

Variation within the species: Numerous varieties of Rocky Mountain maple have been described primarily on the basis of variation in stature, twig color, leaf lobing and size, and fruit shape. The following are currently recognized.

Var. diffusum (Greene) Smiley

Var. douglasii (Hook.) Dippel

Var. glabrum

Var. greenei Keller

Var. neomexicanum (Greene) Kearney and Peebles

Var. torreyi (Greene) Smiley

Distribution: Rocky Mountain maple is broadly distributed in the western U.S., from southeastern Alaska, British Columbia, and southwestern Alberta, south from western Washington to southern California and east to southern New Mexico, northwestern Nebraska, and Montana. For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.