Newswise — A long spell of dry weather during the spring and summer could provide some of the most brilliant colors seen in several years for leaf-lookers headed to the mountains of Western North Carolina this autumn.
The key word is "could," said Katherine Mathews, Western Carolina University's fearless fall foliage forecaster and an assistant professor of biology specializing in plant systematics. Typically, drier weather during the spring and early summer results in a colorful fall leaf season beginning in October, said Mathews.
But below-freezing temperatures in early April " with a severe frost that damaged tender, young vegetation across the mountains " make this year's fall color prediction trickier than ever, said Mathews.
"This certainly has been an unusual weather year for Western North Carolina," she said. "Several nights of hard freeze around Easter weekend killed the new leaves and flower buds on early-emerging hardwood tree species, including the tulip poplars and fruit trees such as apples and pears. The later-emerging species such as oaks were not adversely affected, but the frost delayed the 'greening up' of the mountains overall. It's hard to predict how the response of our deciduous trees will play out this fall."
The killing freeze was preceded by below-average rainfall in March and followed by severe drought in April and May, which is the prime growing season in WNC, Mathews said. "History has shown that fall leaf color is best in years with spring or early summer drought, when plant growth is stunted by a lack of sufficient water," she said. "Depending upon the impact of the late frost on mountain foliage, we may see spectacular color throughout the mountains this fall."
In addition, with increased amounts of rainfall in June and July, most trees are looking healthy as the calendar moves into August, which should prevent early browning and leaf drop, she said.
The final factor in the equation is climate during the first weeks of autumn. "If the temperatures in September and October cooperate and cool down, contributing to the breakdown of chlorophyll, we should expect to see some brilliant fall colors this year," Mathews said.
Chlorophyll is the chemical that gives leaves their green color in spring and summer. As chlorophyll breaks down, yellow pigments " always present in the leaves, but masked by the green of chlorophyll " are revealed, and new red pigments are produced.
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, although leaf browning in tulip poplars the past few months may impact the display of yellow, 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.
Peak fall color should arrive five to 10 days after the first frost at any particular location, Mathews said.
Western Carolina University is one of the 16 senior institutions of the University of North Carolina system. Western enrolls 8,861 students in undergraduate and graduate programs of study, and is located about 50 miles west of Asheville, N.C., near Great Smoky Mountains National Park.
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