Follow the changing aspen in 2017 with Afield

Aspen trees set hillsides aglow in the fall as their leaves turn brilliant shades of yellow, orange, and red. The annual aspen pilgrimage to see the changing leaves is a timeworn autumn tradition for both Colorado residents and visitors to the state. I fondly remember fall trips to the high country dating back to my childhood when my family would attend Rosh Hashanah services at a camp on Mount Evans. I distinctly recall blowing the shofar (a ram’s horn converted into a musical horn) to celebrate the holiday and watching the golden leaves shimmer in the wind around us. Or maybe the leaves were just dancing to the singing and celebration of the Jewish new year. Experiences like this abound among my friends and family in the state and are no doubt common to many Coloradans.

And because we love them so, Afield Trails is highlighting the aspen in Rocky Mountain National Park as Colorado transitions into autumn. The US National Arboretum reports that the brightest fall colors result from a combination of a wet growing season followed by a dry, sunny fall with cool (but not frosty) nights. Luckily, we’ve been spot-on this summer. Fingers-crossed that the weather continues to cooperate.

As part of our aspen-themed fall, we will scout the changing leaves provide reports on current aspen conditions in the Park. Leaves start changing color at high elevations, moving down the slope as the season progresses. High-elevation stands (above 9,500 feet) begin to turn in early September, and the colors run downhill into October. We started monitoring high elevation groves in the last week of August, and plan to provide a weekly rundown of the leaf status, with recommendations on where you can see the best colors that week. You can find our up-to-date weekly reports on the Afield Trails website.

To help you find great hikes with aspen, we added a rating system for the Afield Rocky Mountain National Park app. The rating (0–9) tells you how many aspens are visible on any given hiking route in the Park. For example, the hike to Alberta Falls has a ‘7’ rating, which means it’s a pretty good hike for viewing the fall colors. Watch our aspen report on the webpage for up-to-date conditions of the aspen in Rocky Mountain National Park.

This scoring system only identifies trails that intersect good aspen habitat, but does not gauge when leaves change or how long the colors persist. Many factors determine when a tree’s leaves change colors, including recent weather, available water, and the health of the aspen stand, a suite of data that is too difficult for us to acquire and compute at this time.

If our work helped you find some beautiful places to hike, let us know at

— Aaron Sidder, Editor in Chief