DENVER — It looks like we should see our peak color just a few days ahead of schedule this year. The best color over the northern mountains should be from September 5th to the 15th. The central mountains will be about five days behind, with the southern mountain areas rounding out the last days of the month and the first few days of October.
Perhaps the most appealing part of autumn is the gold found in the mountains each year. Not the gold sought by prospectors over a century ago, but rather the gilded glory of Colorado's famous aspen trees.
The decrease in sunlight switches off the mechanism in the leaves that creates chlorophyll – the green color in the leaf. As the green fades, the gold color dominates until the dying leaf flutters to the ground. The best years for aspen viewing are those with well-timed rains and no major fall storms. A too-dry summer will send the leaves falling quickly, while a wet summer tends to make them darken to brown or black. The most brilliant display of aspen occurs when we have a mild late summer and periodic gentle rain, combined with a dry September that includes few big windstorms or early snows.
Usually the first signs of aspen gold begin in mid-to-late August over the higher forests of central and northern Colorado. By the second and third week of September, many aspen groves are well worth a day's drive. Usually the peak time to view aspen is around the last weekend of September. After that, early snows will knock down the leaves and others drop away by themselves.
Populus tremuloides — or the quaking aspen — can be found in all eleven of Colorado's national forests and their autumn fireworks are worth the drive.