Autumn foliage gets a late start
September 24, 2013
EAGLE COUNTY — Lately, the vistas of the Vail Valley have looked more like a scene from the Pacific Northwest, as opposed to fall in the high Rockies.
Vail and the surrounding mountain areas are known for the brilliant yellow and orange leaves that ignite the hillsides each fall, but this September, the aspens and cottonwoods responsible for the bright colors seem to be hanging onto their greenery a bit longer.
Don't worry — as you may have noticed during the past few days, fall foliage is on its way. Spots of yellow are already popping up, albeit slowly, and the Farmers Almanac predicts that Colorado's leaves will reach their peak color between Oct. 5-14.
That's later than we've seen in recent years. Last year, colors peaked at the end of September, and the leaves went ablaze even earlier in 2011. Naturalists and other experts attribute the later fall colors to a combination of plentiful rainfall and a relatively warm September.
Local naturalist and forager Wolfgang Uberbacher has definitely noticed the delay. Uberbacher is in local forests nearly every day and said he has kept a log of rainfall for years, a useful tool for mushroom hunting.
"Everything is late this year because of the rain," he said. "I've been out there almost every day. Some leaves are actually turning a bit brown. If we don't have cool nights and clear days, what happens is that the leaves go very slowly."
Why leaves change color
According to the Colorado State University Extension office, temperature, sunlight and soil moisture throughout the summer all play a part in how leaves will look come fall. With shorter days and less light in the fall, trees go into energy-saving mode and stop producing chlorophyll. As the chlorophyll, responsible for leaves' green color, breaks down, other pigments called anthocyanins and carotenoids show through. They're there all along, but become visible as the chlorophyll breaks down and are responsible for the yellows and reds of fall.
"Leaves on any tree are expensive," said William Prusse, a forestry technician with the Holy Cross Ranger District. "The tree has to feed them, replace them and keep replenishing chlorophyll. If just one of those aforementioned factors are out of balance, then the tree will shed leaves to reduce the cost to the tree."
This fall is different in that rain has been plentiful since late summer, allowing photosynthesis to continue, and the area has yet to see its first frost.
"The ideal weather for fall colors is a growing season, i.e. summer, with plenty of moisture, followed by a dry, cool and sunny fall with warm days and cool nights," Prusse said.
A shorter color season?
That said, most experts emphasize that it is incredibly difficult to pinpoint exactly when leaves might turn color, how long they'll stay on the tree and what specific factors are in play. However, it is possible that the later color change and abundant rainfall might mean a shorter color season, they said.
"As a disclaimer first, trees don't read scientific papers and can and will act contrary to what we write about them," Prusse said. "With that said, the moisture we have been receiving will cause the trees to keep their chlorophyll longer and thus help keep the leaves that are green or yellow around longer, unless we get a frost. If we get a frost, the leaves will go brown quickly and fall off."
Uberbacher, relying on his fifth sense developed over decades as a naturalist and forager, made a more concrete prediction.
"They will change later and will be less spectacular than years before. Some of them will turn brownish, and I think we might not see some of the bigger colors," he said.
Regardless, Cary Green, of the U.S. Forest Service, said the wacky weather might only make color change vary by about a week.
"Keep an eye on the hillsides, and see how things progress," he said. "The aspen leaves are going to change colors and lose their leaves, to what extent and how long is hard to predict."