AMPLE RAINFALL MEANS LESS COLORFUL LEAVES,
SAYS WESTERN CAROLINA'S FALL FOLIAGE FORECASTER
CULLOWHEE – Abundant late spring and early summer rains across Western North Carolina's mountains likely will put somewhat of a damper on the annual fall color season this year. That's the official prediction from J. Dan Pittillo, the Western Carolina University biology professor who has been christened “the Alan Greenspan of fall foliage forecasting.”
“In a word, leaf color will be below average for the mountains of North Carolina and, in fact, for the state as a whole in 2004,” said Pittillo, a specialist in Appalachian plant ecology who has become a sought-after expert for his yearly predictions of the quality and intensity of the fall color season.
Pittillo bases his forecast on a variety of factors, including the amount of rainfall received during vegetation's prime growing season of the warm-weather months. It's his theory that the best fall color is seen after springs with below-average rainfall, when plant growth is stunted by a lack of sufficient water.
“Rainfall was light from mid-March through May, but much above average in June through August,” Pittillo said. “During the growth period for trees in summer and spring, we saw adequate rainfall. Most of the trees' energy has gone into production of wood instead of producing leaf pigments that yield bright fall colors.”
Also, moist conditions can lead to the formation of fungi, bacteria and mold that can live on the surface of leaves or enter small fissures in the foliage to produce distracting brown spots. “All this activity points toward more subdued color than is usual,” he said.
That doesn't mean that leaf-lookers should expect a total washout in terms of fall color. There should be some scattered sites where the right combination of factors come together to yield good color. “Some folks say there always is good color in the mountains of Western North Carolina if you look around,” Pittillo said.
Development of foliage color is a complicated process and predicting the quality of the color show is an inexact science, he said. Environmental stresses, including precipitation amounts and temperature extremes, are primary factors that determine the intensity of fall color.
The biological process that results in the bright hues of fall is already under way. Cooler nighttime temperatures and the change in the intensity of sunlight as summer gives way to autumn contribute to the environmental stresses that induce the decomposition of chlorophyll, the chemical that gives leaves their green color in spring and summer. As chlorophyll breaks down, other pigments – always present in the leaves, but masked by the green of chlorophyll – are revealed.
Mother Nature's color show will begin first in the higher elevations of the northwestern sections of North Carolina , typically in early October, and progress southward and down slopes through mid-October and early November. Yellow birches, red sourwoods, red and yellow maples, yellow pin cherries and yellow poplars will be the first colors to show, Pittillo said. They will be followed by the yellow and red of oaks and sweet gums, yellow of hickories, yellow and brown of beeches, and a variety of other color shades in the vines, shrubs and understory trees.
Wildflowers always add to the color mix, Pittillo said, with white and blue asters, yellow goldenrods and royal purple ironweeds among the most prominent blooms of fall. “While all of the rainfall means less brilliant colors as the leaves change, it also means healthier, more plentiful wildflowers,” he said.