Fall Foliage... and Leaves 101

Over the weekend the fall foliage assumed a brilliance which signals the height of their show…. and at last the reds arrived! Nature devised leafless trees to give additional sunlight for warmth during the cold winter months and completed this gift with a stunning visual as a parting gift.

Although the following explanation will be a vast over simplification, it may provide insight into the foliage change. During the spring and summer the trees use their leaves to collect air and water utilizing a process called photosynthesis to turn it into food. Photosynthesis means ‘putting together with light’ so as the days shorten and daylight diminishes, the gathering process ends. The leaf is no longer necessary to the tree and begins its fall descent. Suddenly the hillsides are transformed into a dramatic autumn palette that provides breathtaking color for a brief moment in time.

Both the chemicals chlorophyll and carotenoids are present in the leaf cells throughout the growing season with chlorophyll making leaves the bright green color associated with the photosynthesis process. As darkness increases in the autumn, chlorophyll production eventually stops and inevitably all the chlorophyll disappears. With the loss of chlorophyll, the carotenoids become visible and they provide the leaves with lovely yellow colors. Lastly the anthocyanins may arrive and take center stage, ushering in the vibrant reds we associate with Autumn.



Because carotenoids are always present in leaves, the amber, yellow and gold colors remain fairly constant from year to year and will always be available as a spur to the senses. However conditions must be ideal for the fickle anthocyanins, who are glucose (sugar) and singularly responsible for the brilliant hues of purple, crimson, and scarlet. The weather we have experienced this month is perfect for producing their display as it requires warm, sunny days and cool, crisp evenings for without these conditions there will be lackluster reds. An excess of sugar is being produced during these last warm days but the cool nights have slowed the closing of veins going into the leaf and trapped them, thus creating the glorious reds.

However the shade and foliage show are not all the leaves have to offer. They drift from the trees and collect underneath, continuing to work by slowly decomposing over time. By adding their nutrients, a rich soil is created to nourish fledging saplings as they grow to become forest giants like their parents.