The color peak will likely be less dramatic than usual unless the region sees a stretch of sunny days and cold nights in late September and early-to-mid October, Collins said. Some level of stress and cold temperature is required to promote abundant yellow, orange and red pigments in the trees’’ leaves, she said, and such weather has been absent from Western North Carolina this summer.
“The warm, rainy summer caused little drought or ‘hot sunny day’ stress and promoted a lush, full, green leaf canopy,” Collins said. “This is true even in some species we don’t want around. For example, kudzu seems to be overtaking road signs and covering trees at a faster clip than in years past.”
A long-term forecast predicting warmer-than-average temperatures in September and October means that low temperatures around Cullowhee may not reach the 30s until the last week in October — the summer weather pattern might be around for longer than normal.
Fall colors are a mixture of pigments that are revealed as photosynthesis and chlorophyll production wind down and eventually stop as the weather turns cold. These pigments — especially the yellow and orange pigments — play a role in photosynthesis and help protect the plant from stresses; for example, when there is drought, when it’s bright and hot, or under high UV conditions. The pigments are always there in the leaf, but may be relatively less abundant when conditions are wet and warm. The red pigments, called anthocyanins, are also produced more in fall when the weather turns cool.
While a muted fall color display seems likely, Collins acknowledged that, as with any forecast, there is room for variation.
“As we know, local light and temperature conditions vary widely in the mountains over elevation, slope exposure and vegetation type, and there certainly will be areas where colors are brighter or arrive earlier or later,” Collins said. “Sites that typically ‘turn earlier’ are likely to do so again, and colors will progress down the mountain and north to south as they have done in the past.”