VAIL VALLEY , Colorado - Vibrant fall colors that tend to peak in late September should still come to light this fall in Colorado's Vail Valley despite theories that a wet summer might affect the changing leaves.
Annual moisture levels do affect aspen trees, but it's the previous droughts that might impact the colors this fall, said Cary Green, a forester with the U.S. Forest Service based in Minturn.
Past droughts have stressed some aspen groves that could turn brown and shed their leaves before ever displaying fall colors he said.
"We'll see a little of that here," Green said. "But I think it's going to be a normal year (in terms of fall colors)."
Weather is the major player in fall colors, though. The colors will pop when the fall days are warm and nights are cool. Frost temperatures below freezing can delay color changes and also produce less vivid colors, said Pat Slattery, spokesperson for the National Oceanic and Atmospheric Administration.
Tom Gaylord, director of the Vail Nature Center, said he's not expecting a banner year.
"But it won't be a bad year," Gaylord said.
Green leaves on many of the trees are a good sign that leaves will change, he said. When it's really dry, leaves turn brown and fall off before they have a chance to turn yellow.
Too much moisture can also cause a fungus to grow rapidly in aspen trees that can turn leaves brown early, but brown leaves near the Maroon Bells in Aspen are being attributed to insect damage and spider mites.
In the Vail Valley, there is some rust on aspen leaves that may cause dark spots, but that's pretty typical, Gaylord said.
"We should get a gradual change over the next few weeks," Gaylord said.
There are already a few aspen trees turning yellow in the valley, but the reason is usually because of the trees' genetic makeup, according to the U.S. Forest Service.
Aspen trees sprout up from a root system that creates groups of trees that are genetically identical, according to the Forest Service. The chemical balance in each tree is what helps determine the colors of its leaves and when the leaves change color. When there's a patch of yellow trees in the middle of stands of green trees, it's because the trees share the same genetics within their stands.
The length of the day and the temperature is going kick off the colors more than anything, which should happen within the next few weeks, Green said.
Lauren Glendenning can be reached at 970-748-2983 or firstname.lastname@example.org