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Fall in Rocky Mountain National Park is marked by shorter days, cooler temperatures, bugling elk, and the leaves on many species of plants changing colors.
Why Do Leaves Change Color in Autumn?
During autumn, the leaves on Aspen and other plant species change from hues of green to shades of gold, orange, red, purple and brown.
During the spring and summer growing seasons, the leaves of most plants appear green in color as they produce chlorophyll, which supports photosynthesis – the chemical process that allows plants to convert sunlight into sugars for food.
As summer transitions to fall, shorter days and cooler temperatures signal deciduous plants to slow the production of chlorophyll in preparation for winter. As chlorophyll production ends during a plant's growing season and before the plant's leaves fall off for winter, underlying pigments found within the leaves take over and shine with different colors.
Leaves that have carotenoids turn shades of yellow, gold, and orange. Leaves may also have anthocyanins which can turn shades of red and purple.
Factors like elevation, the amount of direct sunlight, soil moisture, and temperature all have an influence on sugar concentrations, which in turn help determine the color of pigments in the leaves during the autumn season. Those same factors also influence how bright those pigments will be.
During the months of September and October, enjoy the many shades of fall colors in Rocky Mountain National Park!
NPS Photo
Aspen trees, as seen in summer with vibrant green leaves.
NPS
This is an example of an aspen leaf that has turned to gold, with pigments of red along the edges.
NPS
This is an example of aspen leaves that have turned red/purple in color.
