Dry summer becomes drab fall
Graphic explains how and why tree leaves change color in the fall; the effects of the drought may be seen in this year's fall foliage because the lack of water makes it harder for the leaves to produce carbohydrates, which are used in the growth process. Chicago Tribune 2012
With HOME-ENV-DROUGHT-LEAVES:TB, Chicago Tribune by Bridget Doyle
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A burning bush turns prematurely red in Winfield, Illinis, on September 21, 2012. Many trees in the region are changing colors early this fall because of stress from drought conditions. (Keri Wiginton/Chicago Tribune/MCT)
CHICAGO — Arborist and “tree doctor” Craig Casino spends his days making house calls and checking on his patients, just like an M.D. This year, his patients aren’t looking very well.
In 40 years of tree care, Casino said, he has never seen weather conditions more devastating than in 2012. Three wetter-than-average summers in 2009, 2010 and 2011 reduced tree roots’ oxygen and water storage capacity, he said. Then, the struggling trees were hit by one of the state’s worst droughts in history, compounding the stress on their root systems.
While memories of the drought might be fading as moisture and cooler temperatures settle in, its impact on trees could play out for years to come. Most immediately the drought may dull the bright leafy reds, oranges and yellows normally expected as the season changes.
“Fall color won’t be as vibrant or as sharp this year,” Casino said. “The trees are changing about four to five weeks earlier this year. The lack of water left them stressed, and now they want to go to sleep.”
Browning, wilting leaves or dropping foliage are signs a tree went dormant in an effort to conserve resources and protect itself, said University of Illinois Extension forestry specialist Jay Hayek.
Trees that didn’t drop their leaves early will still likely display effects of the drought, Hayek said. A lack of water affects the amount of carbohydrates, or sugar, a tree can produce, which in turn affects leaf pigment.
“This year’s fall color will be more drab than years past,” Hayek said.
Hayek said shallow-rooted tree species, such as any variation of Maple, were among of the hardest hit.
The U.S. Drought monitor’s most recent update shows the entire state still under varying drought conditions, though less severe than during summer months. About 40 percent of the state is still in a “severe” drought, according to the map.
The precipitation measured at O’Hare Airport is 7.03 inches below normal, year-to-date, said State Climatologist Jim Angel. June and August were the driest months so far this year at 2.55 inches and 2.83 inches below average precipitation respectively, he said.
September is also proving to be drier than normal, measuring 0.74 inches below normal as of Monday, Angel said.
The National Weather Service Climate Prediction Center is also forecasting an increased chance of above-normal temperatures and below-normal precipitation for October, Angel said.
Angel said trees definitely won’t be as “spectacular” as they’ve been in years past.
“The lack of precipitation pushes leaves to be duller, more to the brown side of things,” Angel said. “The trees want to close up and be done with this growing season.”
Kris Bachtell, Vice President of Collections and Facilities at Morton Arboretum, said drought damage is species-specific. Some trees have clear signs of damage, while other, more resistant species will have a typical fall display, he said.
Those trees living in highly developed suburban areas don’t have a solid root system, making them more likely to show effects of the drought, Bachtell said. Younger trees and those planted in parkways will likely suffer more than those in wooded landscapes, he said.
“Driving around suburbia, I’ve seen pretty severe scorched and tattered leaves,” said Bachtell, who lives in Naperville, Ill. “We’ll likely see fall color early this year - and it’ll be shorter lasting.”
The drought’s impact will go beyond color displays, he said. Many trees that struggled through the drier months are now more susceptible to invasive insects and disease.
“It’s like the trees have a compromised immune system; they’re more prone to fungal disease, ulcers and cankers,” Bachtell said. “Borer insects are drawn to trees under stress because they know they tree can’t counteract or fight as well.”
Casino’s tree house-calls typically come in the spring and relate to invasive species such as Emerald Ash Borer or Japanese beetles. Most trees in urban environments are likely fighting to stay alive because of shallow top soil, he said.
Casino said his best advice to homeowners is to pay attention to their trees - they aren’t as resilient as one might think.
“If a tree’s branches look weak or leaves are discolored and thin, those are early indications there’s a problem,” he said.
Hayek, who works in Urbana-Champaign, Ill., predicts this year’s drought will affect tree vitality five to seven years down the line and, in some cases, could lead to the tree’s premature death.
“We’ll always be able to point back to the drought of 2012 and say ‘this is the reason we’re seeing problems’ in the future,” Hayek said. “(The damage) serves as a source of chronology. Everything that happens in the past affects a tree’s future.”