Fall brings pleasant thoughts of pumpkins and gourds, apple picking, cider & donuts, leaf-raking, hayrides, antiquing, warm sunny days and chilly frosty nights, ghosts, goblins, and Halloween.
Fall is also the season for many chemical changes taking place in our trees – namely, maple, birch, oak, beech, aspen, poplar, and tamarack-each having their own unique chemistries which yield their distinctive leaf colors.
It is believed that their chlorophyll content, which supplies the green color, masks the various hues of red, yellow, blue, purple, orange, and bronze which are always present in the leaf anyway. It is theorized that a pigment in the leaf measures in time the length of nights. When sugar production or oxidation occurs during daylight hours in the summer, it stimulates the supply of chlorophyll. As the nights grow longer, this pigment timer signals the chemical process to produce less sugar, which in turn reduces the amount of chlorophyll, resulting in a pulling back of the green and revealing a display of magnificent colors.
Another thought is that the movement of sap into the tree trunk and roots is affected by the shorter Fall days which in turn deprives circulation to the leaves and eventually affects the chlorophyll production and green color, thereby, allowing the other hues to dominate. Again, a collection of cells located at the end of the leaf stem stops making sugar because they become dry and hard, subsequently depleting the chlorophyll and, therefore, permitting the various colors to shine.
Nevertheless, whatever chemical or physiological changes occur, we don’t need to be too concerned about the “how’s,””why’s,” and “wherefore’s” of them. We only need to take time to enjoy the glorious and vibrant explosion of brilliance which Mother Nature provides-Free of Charge.