By: H. Robertson
Autumn is a beautiful time of year in Maryland. The leaves begin to change early October and sometimes late September. The timing of color change and leaf fall dependson the increasing night length. The first I notice are the red maples turning brilliant red or yellow. They are also the first to leaf out in the spring. One can always tell a red maple by the red petioles.
First we see yellows, oranges and reds.Why do the leaves change color in the fall? Basically the trees need time to acclimate and toughen up for winter.
Deciduous leaves are too thin to survive cold temperatures in winter. The leave’s chlorophyll, which gives the green color, starts to breakdown as the days get shorter and the nights longer. The green eventually disappears and the yellow and orange carotinoids begin to show. When it gets cooler, sugars stored in the leaves turn a reddish color and the red/purple anthocyanin pigments develop. This usually happens after the days have been shorter for a while, and the nights are increasingly cooler.Soil moisture also determines the brilliance of the color along with temperature. Bright days and cool nights give the best color. We see scarlets and purples last, sometimes after many other trees have lost their leaves.