True Colours

Day 5: With the onset of Autumn, trees and shrubs reveal their true colours. Yes, you read that right. Now, shorter days and cooler temperatures slow down the flow of nourishing carbohydrates and chlorophyll production is reduced. As existing chlorophyll breaks down, the natural colours of the leaves are no longer obscured by green and begin to shine through in all their glory. Eventually, a hard abscission layer is formed where petiole meets twig and, generally speaking, the leaf drops. Deciduous trees and shrubs are not all alike in the types of pigments present in their leaves. Those which turn red in Fall are long on anthocyanins. Large amounts of xanthophyll are present in those which turn yellow. Leaves which turn orange contain carotene. These pigments are not immune to shorter periods of sunlight and colder temps, though, and eventually even they will succumb and turn brown. Some leaves may hang on until the following spring. This phenomenon is called marcescence, and it will be the subject of a future post.