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Habersham County
The Mountain Traveler • Fall 2013
Yellow and orange in leaves is caused when green fades at the onset of autumn. File photo
experiencing wet weather going into fall, according to Paul Pastelok, senior meteorologist and head of AccuWeather’s long-range forecasting team. “Though the frequency of flooding events will scale back from that of the summertime, the threat will hold through the fall due to the collision of stronger cold fronts and tropical moisture,” Pastelok stated. The threat for tropical storm development could linger late in the season. “The bulk of these systems will come in September and probably early October, but it looks to me that we’re heading into a late season with a storm here and there through November,” Pastelok said. Having wet fall weather “mostly effects the formation of red as the weather gets cooler,” Mathews said. Tree species which have red coloration “may not be as bright a red,” Mathews said. “They need a lot of sunshine for good development.” The yellows and oranges in leaves are a product of the photosynthesis process [carotosysis] and consequently when the green fades away in autumn, the yellow and oranges remain. Production of red coloration still holds mystery for scientists, according to Mathews. Production of red is not a part of the photosysnthesis process, but photosynthesis produces the sugar needed to produce red color. If wet conditions do not allow production of sugar, then production of red color is limited. “If there is not
as much photosynthesis, then there is not so much sugar to produce red,” Mathews said. Temperature and the amount of daylight are other primary fall color factors. If temperatures remain mild and there is no frost or low temperature, a color peak is not triggered, Mathews said. A color peak is “maybe five days after a frost,” Mathews said. Mild temperatures mean a “gradual, slower change in color.” Mild temperatures could also mean a longer leaf season, albeit with muted colors. Still, if October is dry, “that should help,” Mathews said, of leaf colors being more vivid because trees “would have more time to make red pigment.” The search for a leaf peak may be found in higher mountain elevations which experience a greater likelihood of colder temperatures during autumn nights. “Those areas may have the chance of seeing temperature in the 30s in the evenings,” Mathews said, especially mountain peaks above 5,000 feet.” Trees signaling the beginning of fall color are fruit trees, locusts, sourwood, black gum and sumac. In the middle of the fall season, poplar offer yellow hues for display. Maples provide the vivid scarlet often associated with the fall season. The leaf-looking season winds down with the turning of oak leaves. n