Aspens in fall. Photo: Clinton Bellingar

Planning Your Fall Foliage Experience

Photo: Nancy Dadisman

Heading to the mountains for some leaf peeping? Be sure you pick the best weekend!

Timing peak aspen colors each fall is an imperfect science, and the ideal time and place one year can turn out to be a disappointment the next. The reason aspen leaves change, like the leaves of any deciduous tree, is because of a decrease in photosynthetic activity as the days get shorter in the fall.

The gold and yellow colors we see in autumn are always there; in the fall, they simply are revealed when the green hues from chlorophyll production fade. Recent local weather conditions, available moisture and stand health all influence those expansive golden vistas.

According to the United States National Arboretum, a wetter growing season followed by a dry, sunny autumn with cool but frost-free nights results in the brightest fall colors.

Also, stand health is a critical factor for aspens to display strong colors and retain leaves later into the fall. Unhealthy aspen stands are less likely to have vibrant colors, and the more robust an aspen stand is, the more attractive its colors will be.

While the complexity of these factors may make it difficult to schedule your trip, a few easier-to-predict factors such as elevation and latitude impact the timing of peak leaf change.

Through September and early October, higher-elevation stands and those that are farther north will show colors sooner than lower, more southerly locations.

Aspen Facts

  • Make up 20 percent of Colorado’s forests
  • Elevation 6,500 – 11,500 feet
  • Grow in clones of genetically identical stems
  • Healthy, mature root systems put out up to 1 million shoots/acre
  • Stands thin themselves as they mature
  • Grow up to 10 feet tall in five years; fast-growing compared to native evergreen trees
  • Commonly known as “quaking aspen”
  • Flat rather than round stems allow leaves to flutter
  • Stems give leaves strength, allowing them to twist in the wind
  • Bark contains salicin (similar to the active ingredient in aspirin); pioneers and Native Americans used as a fever remedy