Fall color update: Leaves not so hot due to storm systems, warm October

Two major storm systems and unseasonably warm October temperatures have conspired to dampen what was widely expected to be one of the most vibrant fall color seasons in recent memory.

That’s the updated viewpoint from Western Carolina University’s autumnal season sage Kathy Mathews, who makes an annual fall foliage forecast regarding the quality of the upcoming color show in the mountains of Western North Carolina.

An associate professor of biology at WCU who specializes in plant systematics, Mathews bases her prediction in part on weather conditions, including rainfall, during the spring and summer growing season. She believes that the formation of higher levels of pigments in the leaves correlates with dry weather throughout the year, especially in September. The drier the climate, the more brilliant the fall leaves tend to be, with bright red colors especially dependent upon dry conditions, she said.

Kathy Mathews

Kathy Mathews

Drier-than-normal conditions during much of the 2015 growing season had Mathews calling for bright fall leaf color back in August. But then two weeks of stormy weather hit the mountains in early October, dramatically altering the outlook.

“I believe the heavy rains and wind we experienced the first week of October were a detriment to the fall color development, which had been proceeding nicely until then,” Mathews said. “I was hoping this would not be the case, but now I think it is. A lot of leaves appear to have been lost at that time, and the colors were very drab looking afterward.”

In addition, the rains were followed by a warming trend, which delayed the degradation of chlorophyll – the pigment that gives leaves their green color in spring and summer, she said. The yellow and orange hues of fall result from other pigments that the leaves make year-round but that are hiding under the green color of chlorophyll. As days get shorter and nights get colder, the chlorophyll breaks down to reveal the pigments underneath.

“The extended warm temperatures allowed the chlorophyll to persist, muting the other pigments that provide the colors,” Mathews said.

Many areas of the mountains have had frost, and Mathews said she expects colors will begin to peak this weekend (Oct. 24-25.)

“There looks like there still is going to be good color in some places, but it will be spotty, as a lot of trees have lost many of their leaves already,” Mathews said. “I think that color change will continue into early November, particularly in the lower elevations.”

Regardless of when the peak occurs and how intense the hues are, visitors always can find good fall color somewhere in the WNC mountains, with more than 100 tree species in the Southern Appalachians, she said.