Why the Leaves Turn Color in the Fall

The turning leaves of deciduous trees are a welcome sign of autumn and its longer, cooler nights. Vibrant reds, yellows, and oranges make up the color scheme of fall, and they are all part of the cyclical nature of the seasons. Leaves on trees, shrubs,and plants turn colors when they begin the process of going dormant for the winter and before the white stuff starts to fly.

Once the days and nights begin to cool and the nights get longer, the trees sense that fall and winter are approaching. In the trees' preparation to go dormant, circulation to the leaves, which are no longer needed to produce food, is cut off. Due to the long nights and reduced sunlight, the production of chlorophyll is reduced, meaning that the green will eventually disappear fromthe leaves. Some of the pigments responsible for causing the vibrant colors in the leaves, such as carotenoids, are in the leaves. but are obscured by the green chlogophyll. Carotenoids are responsible for yellows, orange and browns.

The trees in the Sawtooth range of southern Idaho, the Wasatch of northern Utah, and the Rockies of Colorado are turning now and will reach their peak this month into the first part of October.