If you’ve noticed trees with early fall color, you’re not alone.
“Right now, we are definitely seeing more widespread color early on compared to last year. It’s definitely ahead of schedule a bit, and a lot of that is driven by the dry weather we have had,” said Christy Rollinson, a forest ecologist for the Morton Arboretum in Lisle.
Most of the Chicago region is in what’s called a D1, or a moderate, drought, according to a U.S. Drought Monitor map released last week. Late season droughts are typical, but this year’s has been deeper and longer, said Pati Vitt, director of natural resources for the Lake County Forest Preserve District.
“Some trees, maples for example, seem to be transporting their chlorophyll a bit earlier than usual, and I’m seeing them start to turn colors a bit sooner than might be typical, especially at the branch tips, at least in some places,” she said.
Leaves from a River Birch tree are drying up and falling to the ground in Woodstock.
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So what does all that mean for prime fall color? When will the hues of autumn hit their peak?
It’s a hard question for experts to answer. When trees change color is highly driven by individual tree characteristics, including what species it is, Rollinson said.
Particularly “as we start getting into October and mid-to-late October, it’s really what happens from day to day that determines what trees are going to peak and when,” she said.
The intensity of colors
At the arboretum, a place devoted to trees, Ed Hedborn, manager of plant records, writes a weekly fall color report. Hints of fall color can be seen in parts of the arboretum’s tree collections and woodlands, according to his latest report.
“These changes are mainly the result of stress on trees from heat and dry weather this summer and fall,” Hedborn wrote last week.
Said Rollinson: “Right now, we are starting to see color on a lot of trees, including maples, which are often some of the real stars of the fall. But other trees that can still produce good color, like oaks, are still a ways off.”
If there is sufficient rain and nighttime temperatures are cool and days are warm, that combination will allow plants to develop brighter and longer-lasting colors, Hedborn noted.
Trees start to shut down their growth as the nights get longer.
“It’s all chemistry,” said Barb McKittrick, environmental education manager for the Forest Preserve District of Kane County.
The USDA Forest Service explains the chemistry: Chlorophyll is the green pigment in leaves. Carotenoids are also present in leaves and result in yellow, orange and brown colors when chlorophyll production stops. A third pigment is anthocyanins, which results in a red hue.
One tree is changing colors while others hang onto summer green Monday in Glen Ellyn.
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Bright, sunny days will help promote the red color in trees such as red maples, Rollinson said. That red pigment is actively produced by some trees to help them as they are breaking down the nutrients from the leaves and storing those nutrients for next year.
Drought relief?
Rain this past weekend was welcome, but “it wasn’t likely enough to have an appreciable effect on the display, which generally tends to be shorter in duration and not as intense during drought,” Vitt said.
However, the effects will be very localized, so there may be some places with a better display than others, Vitt added.
Maple leaves are drying up and hitting the ground in McHenry County.
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“Unfortunately, once you do hit that drought destination, it typically requires quite a bit of rain to kind of overcome it. But we did get a really great soaking rain yesterday, so that’s probably going to cause some trees to change color more slowly,” Rollinson said Monday. “And if we get … the rain we have coming, it’ll continue to kind of push off some of that fall color.
“And some of the things that haven’t started really turning yet, they might still put on a really great color show for us.”