Saint Vrain Canyon
Lake Granby in fall
Autumn aspen in early fall snow in the Poudre Canyon
Blue Grama grass turns colors on the Pawnee Grassland in the fall.
Guanella Pass is spectacular in the fall.
Why Do the Aspen Leaves Change Color?
Summer aspen leaves are green and full of chlorophyll until the day lengths shorten. As trees become dormant, the chlorophyll lessens in production, but leaves behind carotenoids, which causes the orange or yellow color. The carotenoids in aspen or other deciduous trees is what creates the colors in carrots, oranges, and bananas, or red anthocyanin in cranberries and apples. The leaves will remain on the tree until they fall off from high winds or frost damage.