• Hinds, T. E.
  USDA Forest Service
  
• Krebill, R. G.
  

Aspen (Populus tremruloides) reaches its most magnificent development in the Rocky Mountains, where trees often live to more than 200 years and become forest monarchs. On the better sites it frequently attains heights greater than 100 feet and diameters of more than 2 feet. At its lower elevational limit, aspen is often a scrubby tree found principally along creeks flowing through ponderosa pine forests or shrublands. Still, aspen may grow to timberline (as high as 12,000 feet in elevation) where it takes the form more of a shrub than a tree. Although it is of slight economic importance for wood production throughout most of the West, aspen is appreciated as one of the most esthetically pleasing trees of western mountains and is a favored habitat of diverse wildlife species.