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The Fall Color Show
Researched and Written by Janine Weins
(Posted 9/6/06)

Before the winter cold sets in and the fields are covered with white snow, we are treated to a spectacular color show as the leaves of the hardwood trees change from green to a mix of reds, oranges, yellows, and browns.

During the summer the leaves of the maple, poplar, oak, box elder, locust, birch, and other deciduous trees contain chlorophyll and carotenoids. In the late summer a third pigment, anthocyanin, is produced. Chlorophyll is green, carotenoids are yellow, orange, and brown, while anthocyanin is red.

When the days are warm and long, in a process called photosynthesis, the green chlorophyll uses energy from the sun to transform carbon dioxide and water into sugars and starches that nourish the tree. In the winter, leafless hardwoods take a break from photosynthesis. Between the green leaves of summer and the bare twigs of winter there is a color show.

As the days get shorter and the temperatures cooler, the leaves produce less nourishment and the chlorophyll in the leaves begins to break down. When the days are warm and the nights are too cool for the nutrients produced during the day to flow through the fine veins in the leaves, anthocyanins are formed. As the photosynthesis process shuts down, the leaves lose their green chlorophyll and take on the colors of the carotenoids and the anthocyanins that remain in the leaves.

Colors vary with the species of trees. The most popular fall foliage trees are sugar maples that often have bright orange-red leaves. Poplars have glowing yellow leaves. Oak leaves are red, brown, and russet. The box elder turns a greenish yellow while black locust leaves are a yellow or brownish green. When I was a kid, we had many big birches; there are now fewer birches and they are smaller, but their yellow leaves still look beautiful against the white birch bark.

The weather helps to determine the fall colors. My favorite fall weather—warm sunny days followed by cool crisp nights—produces anthocyanins, the red pigment, that is required for the best foliage colors. A wet spring helps to produce large healthy leaves that hold their color. If the fall is particularly wet, colors appear duller, almost as if the rain has diluted the pigments. The best foliage colors come after a wet spring, a dry fall, and early September days that are bright and sunny with cool, crisp nights.

Even the best of fall foliage seasons can be ruined by a single weather event such as a severe frost or strong winds, both of which can cause the trees to lose their leaves.

On my hill, the trees have begun to shed their summer green. Every few days I notice more color in the surrounding hills. A special way to enjoy the colors of the season is to plan three or four driving trips during the next few weeks over the same route, or if you are fortunate enough to have a colorful view, take a picture every day from the same location.

Two special ways to view the fall foliage are from a hot air balloon (802-333-9254) out of Post Mills Airport in Vermont or from The Hobo Railroad (603-745-2135), which offers daily trips from Lincoln, New Hampshire.