Although frequent rain may be good for growing grass, it can also mute the expected brilliant hues of trees as the season changes. According to two West Virginia University experts, heavy precipitation and warmer temperatures are responsible for the lack of colors seen this fall.
“A tree doesn’t ‘want’ to drop a green leaf, since that leaf is full of stuff the tree can use— stored nutrients and energy. Trees are trying to scavenge back all they can from leaves before freezing temperatures set in. That scavenging process starts due to cues, including the length of daylight and weather, both in the growing season and the autumn. When there are bright sunny days followed by cool nights in September, we tend to have more color change, rather than when days are cloudy and gray, and nights are warm, such as we’ve had this year.”
Interim Director of Plant and Soil Sciences
Associate Professor of Horticulture
WVU Davis College of Agriculture, Natural Resources and Design
(304) 293-2944; Sven.Verlinden@mail.wvu.edu
“There are some pigments that are being unmasked in the fall, and others that are being produced by the trees. During the regular year leaves are green and there is actually yellow pigment underneath (carotenoids). In the fall, chlorophyll (green pigment) basically disappears and some of the nutrients in the leaves are being recycled back into the tree and that unmasks their yellow color. In the fall, the trees also start producing anthocyanins, another pigment that is mostly reddish in tint. This works really well when the weather cooperates. Now, we’ve had quite a bit of rain this year and that works against it. And we haven’t had good temperature swings between day and night.”
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