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September 7, 2010

MADISON - Autumn 2010 is shaping up to be a wonderful time to get outdoors to appreciate the state's forest resources and to view Wisconsin's version of colorama.

"Department of Natural Resources foresters throughout the state are just starting to see the beginning of colors at various locations in the state," according to Virginia Mayo Black, a communications specialist with the Forestry Division. "While fall color is very much determined by local conditions, the shift to fall weather patterns means Colorama 2010 will be debuting very soon."

Although the official start to autumn begins on September 23, it's the daytime and overnight temperatures that really control when leaves will turn red, yellow, purple, and orange.

"A series of days with cool nighttime temperatures and sunny days will result in the brightest fall foliage colors," Mayo Black said. "It's been a warm and wet summer in Wisconsin this year, but cooler nighttime temperatures are now starting to replace the hot and humid weather forecasts."

According to the Wisconsin Department of Tourism's Fall Color Report (exit DNR), autumn tree color is in the 0-to-25 percent range. But anyone traveling in the state has probably spotted a few trees in both rural and in urban areas starting to change color.

'That's not an unusual situation," Mayo Black said. "If a tree has been stressed by extreme weather or by physical conditions like compacted soil or some form of damage or if a tree is not healthy, the tree's leaves may turn color earlier than usual. For at least the past 7-plus years, areas of Wisconsin have experienced drought conditions. This year, there have also been areas of the state that have gotten a lot of precipitation. It's that combination of stressful growing conditions most likely accounts for some trees turning color well before the official start of autumn."

Based on reports from DNR foresters throughout the state, colorama will probably start "in earnest" after the first week in September."

A tree's leaves change color in Wisconsin and other temperate-climate states in response to decreasing exposure to sunshine coupled with cooler night temperatures. Leaves get their green color from chlorophyll, a pigment that enables a tree to process sunlight, eventually converting the other chlorophyll and other chemicals in the leaves to food for the tree. Once autumn weather conditions start, the chlorophyll in a tree's leaves stops being manufactured, and other chemicals in the leaves (the carotenoids and xanthophyl that result in leaves changing from green to yellow, orange, and brown and the anthocyanins that result in red and purple leaves) become visible.

So when is the best time to see fall color in Wisconsin?

"Generally speaking, peak colors start to develop in mid-to-late September in northern portions of the state and can continue into October and the first half of November," Mayo Black said. "The one thing that will cut colorama short is a big wind-driven rainstorm moving through an area and blowing the leaves off of the trees."

While there's no absolute way to predict when trees will turn colors or how long the display of autumn colorama will last, Mayo Black said fall in Wisconsin offers multiple opportunities to enjoy the state's 16 million acres of forestlands and its millions of urban trees.

"Autumn is always a breathtaking time in Wisconsin, and Badger State residents are fortunate to live in a state where the seasons change," Mayo Black said. "Whether it's going for a ride in the country, spending time camping at a state forest or park, walking through a woodlot or natural area, or taking a walk walking through a neighborhood or local park, fall is a great time to get outdoors to view and appreciate the state's rural and urban forest resources."

FOR MORE INFORMATION, CONTACT: Virginia M. Mayo Black, 608.261-0763.

Last Revised: Tuesday, September 07, 2010

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