The aspen is found across North America due to its ability to grow in virtually all mountain vegetation zones. According to the U.S. Forest Service, aspen forest is most common in Colorado and Utah at elevations between 5,000 and 12,000 feet.
The tree grows best in the "moist but well-drained, slightly acidic soil found at higher elevations," writes Robert Cox, horticulture agent at the Colorado State University Cooperative Extension.
Aspen do not tolerate shade and can sprout in full sunlight.
Aspen trees can quickly colonize areas ravaged by fire. "In the Central Rocky Mountains, the extensive stands of aspen are usually attributed to repeated wildfires," writes the U.S. Forest Service.
Plant Talk Colorado, a publication of Colorado State University, says that aspen planted in urban settings do best on the north and east sides of buildings. However, it adds that aspen are generally difficult to grow in the urban landscape because the soils they like are rare and because of their susceptibility to disease and insects.
In recent years, aspen stands in several Rocky Mountain states and Canadian provinces have suffered a sudden die-off. According to a Reuters story from Sept. 4, 2009, scientists at the Rocky Mountain Research Station in Moscow, Idaho, predict the near total disappearance of aspen in the Rocky Mountain region by 2090, due in large part to global climate change.