Conifer Trees Database

Abies lasiocarpa var. bifolia, as described in 2009 by James E. Eckenwalder in Conifers of the World, The Complete Reference, is commonly known as the western or Rocky Mountain subalpine fir.

Description. Rocky Mountain subalpine fir differs from the typical species in the following ways

• Fresh leaf scars on var. bifolia reveal a yellow or tan periderm. On var. lasiocarpa, the periderm is red.
  
• On foliar buds, the basal bud scales are long, narrow-triangular to spathulate with crenate to entire margins.
  
• Leaves are 0.4 to 1 long by 0.06 inch wide (11 - 25 × 1.25 - 1.5 mm); when crushed they have an odor similar to camphor (less sharp of a smell than the type); lower needle surface has 3 to 5 lines of stomata on each side of midrib (4 to 5 on each side in the type); upper needle surface is light green to blue-green, usually glaucous, with 3-6 rows of stomata at midleaf.

Distribution. This variety occurs in Canada - southern Yukon, Northwest Territories, Alberta, and British Columbia; in the United States - Washington, Oregon, Idaho, Montana, Wyoming, Colorado, New Mexico, Arizona, Utah and Nevada at elevations of 2,000 to 12,000 feet (600 - 3,700 m) above sea level in subalpine conifer forests. Var. bifolia is found growing to the alpine treeline in most of its range. In most of the Rocky Mountains, it forms a major forest type with Picea engelmannii