Rocky Mountain Maple

Acer glabrum

Species distinguishing characteristics: 

  • Reddish twigs with opposite branches
  • 3–5 lobed, typical maple leaves
  • 2 tan colored, winged seeds joined at the base in a V-shape
  • Smooth, grayish-purple bark on older shrubs/trees
  • Few flowered clusters of yellowish-green flowers

Family Characteristics: 

  • Deciduous trees or shrubs.
  • Opposite leaves often appear like typical maple leaves
  • 2-winged seeds
  • Flowers with 4–5 sepals and petals (petals sometimes lacking) 
  • Male and female flowers on separate trees

Growth habitat: 

Short-lived, deciduous shrub to small tree to 7 m (or 9 m) tall.

Leaves and stems: 

One to many trunks.  Slender, greenish-brown twigs turn reddish during their first winter.  Branches and leaves are smooth, arranged oppositely, 2–10 cm wide, and have 3–5 lobes like a typical maple leaf.  The middle lobe is sometimes divided further into 3 lobes, and the whole leaf is sometimes deeply lobed.  Leaves are paler on the underside.  Leaves turn yellow-orange to red in autumn.


Thin, smooth, reddish-brown bark becoming grayish-purple when older.


Male and female flowers on separate trees and appear when leaves open.  Loose, drooping clusters of about 10 fragrant, yellowish-green flowers, 5–10 mm across, at branch ends.  Flowers have 4–5 petals and sepals.


Pair of slightly spreading, winged seeds (samaras) join at the base in a V-shape and hang from slender stalks.  Wings, 1.5–3 cm long, are light green, tinged with rose when unripe, and turn straw-colored when mature.

Habitat preferences: 

Open coniferous forests and clearings, thickets, stream banks, seepage areas, and floodplains at low to subalpine elevations.  Prefers south aspects and well-drained soil.

Interesting facts: 

Heavy use of this winter browse by hoofed mammals often results in shrubs that look as they have been overzealously pruned.  Dried, fallen leaves can be packed in boxes with apples and root vegetables to preserve them.  The pliable bark has been used for tying and weaving.  Many tribes valued the durable wood and soaked, heated, and shaped it into digging sticks, snowshoe frames, bows, and tool handles.  Some tribes highly prized the wood for making arrow shafts.  Bright crimson, velvety patches on the leaves are usually caused by harmless infestations of eriophyid mites.

Biological Classification: