Ample rainfall means less colorful leaves, says Western’s fall foliage forecaster

CULLOWHEE – Plentiful precipitation during the late spring and early summer across Western North Carolina’s mountains is expected to result in a less spectacular display of autumn colors this year.

That’s the official prediction from Western Carolina University’s new fearless fall foliage forecaster. Katherine Mathews, an assistant professor of biology specializing in plant systematics, is taking over the duties from longtime prognosticator J. Dan Pittillo upon his recent retirement after nearly 40 years as a faculty member in Western’s biology department.

Mathews said she has some big shoes to fill, as Pittillo became widely known as “the Alan Greenspan of fall foliage forecasting.” A faculty member at Western since 2003, she is basing her predictions about the intensity of fall color upon Pittillo’s 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.

“In a nutshell, fall leaf color will not be especially spectacular for the mountains of Western North Carolina and, in fact, for the state as a whole in 2005. Rainfall was light in January and February, and again in May, but was considerably above average from June through August in the mountain areas,” Mathews said.

“Historically, we see the brightest color when we experience periods of dry weather during the trees’ growing season. Lack of rainfall stresses the trees, and that stress typically results in more colorful foliage,” she said. “During periods of adequate rainfall, most of the trees’ energy goes into production of wood instead of producing leaf pigments that yield bright fall colors.”

That doesn’t mean that leaf-lookers will be totally disappointed in the display of fall color, Mathews said. There should be scattered sites where the right combination of factors come together to yield good color.

“Even during an average year, the mountains during the fall season are pretty impressive,” she said.

The biological process that results in the bright hues of fall is well 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.

The annual 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, Mathews 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 smaller trees beneath the forest canopy.