The Colorado blue spruce is the state tree, but it is the quaking aspen that is the best known and most easily recognized tree in Colorado. The “gold rush” occurs every fall as millions of people are lured to the high country to view the beautiful colors of changing aspen. This member of the poplar family, which grows at elevations ranging from about 6,000 feet to almost 11,500 feet, can be found in all of Colorado’s national forests — but nowhere in Colorado can one see as many acres of aspen as on the drive over Kebler Pass. The color change in the high country starts in the middle of September and lasts into October, depending on temperatures and weather conditions. On a clear, cool September day, the combination of blue-gray and pure white of snow-capped peaks, yellow to red-colored aspen, and rich blue skies can easily cause a sensory overload.