Spring blossoms with hope, summer peaks with flora and fauna, and autumn bursts with color.
The leaves are beginning to change in the Midwest. A new splattering of vibrant yellows, oranges, and reds is seen everywhere we look. It’s like fireworks shooting a new display every day.
The process of leaf changing is fascinating. Much has to do with the declining hours of daylight and the types of trees. Aspen leaves turn bright yellow; oaks’ turn red or brown; dogwoods’ turn purplish red or light tan; and some of the maples’ turn brilliant scarlet. Others, such as elm leaves do not change at all. They simply die and fall off.
For the trees with leaves that do change, leaf color is influenced predominately by the shortening of daylight but also by pigments in the leaves and weather. For optimum color, leaves require a warm, wet spring, favorable summer temperatures, and warm, sunny fall days with cool but frostless nights.
During the spring and summer, the trees take in water from the ground through their roots and carbon dioxide from the air. They use sunlight to turn the water and carbon dioxide into oxygen and glucose in a process called photosynthesis.
There isn’t enough light or water in the winter for photosynthesis. The green chlorophyll disappears from the leaves revealing the yellows and oranges that until then were present but unseen. The cool nights of autumn turn the glucose bright reds and purples.
Unlike the tender leaves of deciduous trees, the tough needles of evergreens with their heavy wax coating and fluid inside their cells resist freezing and withstand severe winter conditions.
(Information gathered from the U.S. Department of Agriculture)
©2014, Mary K. Doyle
Midwest Mary 