In the wake of the 2012 drought, one questions that remains is: How will it affect fall foliage colors?
The deep reds, crisp oranges and golden yellows that usually punctuate the fall landscape may not be so spectacular this year after a summer of statewide heat and drought.
"Drought is bad for fall colors," said Jeffrey Dawson, a professor emeritus of natural resources and environmental sciences at the University of Illinois. "In a normal fall season with plenty of rainfall, the leaves should begin to change in October. In a fall season such as this one, we are seeing a premature leaf drop. This affects fall colors because with leaves falling from the trees earlier, fewer leaves are left to actually change color."
Even though the summer drought has affected the health of Illinois trees, state climatologist Jim Angel remains hopeful that fall colors will still be able to make an appearance this season.
"All is not lost - the recent rains and cooler weather have slowed the deterioration of the trees' health. I'm a little more optimistic now than I was a month ago.
"Predicting fall color is still more art than science," Angel added. "The best recipe for good fall color consists of a growing season without stress (such as that brought on by drought, flood, heat), followed by fall that has clear, sunny days and night temperatures that are crisp but not below freezing.
"You do not want a wet, stormy fall because the cloudy days and wet leaves cause the colors to be muted," he said. "In addition, stormy weather has a habit of blowing the leaves off trees just as they turn color."
Dawson said the color-change process is a living process.
"During the period of color change, sugars and other nutrients from the leaves move back into the tree, allowing it to retain (sugars and nutrients) efficiently, rather than shedding them with subsequent leaf fall."
"For the first time since 1988, all of Illinois has experienced drought this year," Angel said. "So the results are going to be similar around the state."
Angel is affiliated with the State Water Survey, a unit of the Prairie Research Institute.
Not all experts agree with the dry-means-dull prediction. Conventional wisdom is that dry weather means a duller fall. But reality may be more complicated than that.
Trees in some regions may actually put on a better fall foliage show than usual this year because lower-than-average levels of rain may lead to an earlier retreat of chlorophyll, the green pigment that allows plants to harness the sun's energy, said Donald Leopold, a tree researcher at the State University of New York in Syracuse.
With chlorophyll gone, other pigments in leaves become visible. These include carotenes and xanthophyll pigments, which appear yellow to orange and are present during the growing season but are masked by the green.
Temperatures in southeastern Illinois and elsewhere in recent days have begun to dip into the 30s some nights. Colder temperatures and shortening days serve as signals to plants to begin reducing the amount of chlorophyll produced and to start preparations for winter, which involves moving sugar and nutrients from leaves to roots.
Sufficiently cool temperatures can also directly reduce the amount of chlorophyll produced. Without being continuously renewed, chlorophyll breaks down and eventually leaves will fade from green to yellow or red.
Leaning toward the drought-means-dull interpretation, AccuWeather.com reports that while some portions of the Northeast have a chance at vibrant fall foliage based on forecast weather, drought-stricken parts of the country may not have much of a display.
For southeastern Illinois, the normal peak times for fall color are mid- to late October, according to the Weather Channel's fall foliage map.
There are many places to get fall-color information. The U.S Forest Service's toll-free Fall Color hotline can be reached at (800) 354-4595. The automated line provides national forest visitors with weekly updates on fall foliage color changes and fall activities throughout the nation, and could give travelers an idea of what to expect nearby.
And in Indiana, the Hoosier National Forest Web site has fall-color information about southern Indiana, including suggested driving routes, at http://www.fs.fed.us/r9/hoosier/docs/fallcolor.htm.
One of the most-often-updated places on the Web to find fall-color information is the Weather Channel site, www.weather.com. A quick link to its fall-color map page is at the University of Illinois Extension fall color site, http://www.urbanext.uiuc.edu/fallcolor. Click on "Foliage Updates," then "Normal Peak Times for Fall Color." Choose "U.S. Current Fall Foliage" in the list below the map to get a current report.
The Extension Web site has many other links to foliage reports, live webcams, scenic drives, photos and much more.
For a few weeks, nature puts on one of its most spectacular displays as native trees and shrubs finish out the growing season in a brilliant display of fall colors.
Jack Frost usually gets credit for the beautiful colors, but, in reality, fall color is controlled by both the plant's genetic factors and the environment, according to Barbara Larson, University of Illinois Extension horticulture educator. Carotene and xanthophyll are yellow pigments produced in foliage all year; along with chlorophyll, the green pigment. In autumn when short days and cool temperatures slow down the production of chlorophyll, the remaining chlorophyll breaks down and disappears. Then the yellow pigments that have been masked by chlorophyll show up. These pigments give the ginkgo its clear yellow color. Redbud, larch, hickory, birch and witch hazel turn hues of yellow and gold.
Some plants produce anthocyanins (red and purple pigments) that may mask the yellow pigments. Some maples, dogwood, black tupelo, oaks and winged euonymous seem to be on fire with red and purple.
"Trees and shrubs need to go into the fall without a lot of stress from disease or severe drought," State Climatologist Jim Angel said. "Chilly, not frigid nights and cool, sunny days enhance the changing leaf colors. Detrimental conditions include extended periods of rain or cloudiness that mute colors, high winds that blow leaves off trees, and hard freezes that stop color changes entirely."