EAU CLAIRE — Mostly dry conditions and warm temperatures are behind the less-intense fall colors in the Eau Claire area this year, according to the state Department of Natural Resources.
“We do see a lot of muted color this year, which is an indication that the warm temperatures are pushing off that color change,” said Colleen Matula, a forest silviculturist and ecologist with the DNR.
In much of Wisconsin, September brought daily high temperatures largely in the 70s and 80s.
Eau Claire County also experienced a moderate drought from early June through July, though dry conditions eased in August, according to U.S. Drought Monitor maps.
“Sometimes drought can really delay fall colors, or they won’t happen at all, like in the northwestern part of the state near Ashland, ” Matula said. “We’ve had a drought and that has really significantly impacted our colors.”
Matula also believes that peak color might come a little later for the Eau Claire area — but storms could also impact the color forecast.
“We need the cool nights to bring on that vibrancy of colors,” she said. “I don’t know if that’s going to happen. I think we’re starting to lose our leaves due to some rain or wind events. Pretty much all over the state we’ve been seeing this.”
Matula said warm weather in the fall also encourages exotic tree pests to flourish, putting some trees under additional stress. Those pests include the emerald ash borer, an invasive wood-boring beetle that targets ash trees, and pests that target aspen and birch trees too.
“That will impact fall colors as well,” Matula said.
Nearing peak color
Most of the Chippewa Valley is at or near peak fall color, according to the Travel Wisconsin 2021 Fall Color Report.
The report says Eau Claire is at about 75% of its color peak as of this week — the area is estimated to hit peak color in the third week of October. Chippewa County is at about 70% of its peak, and Menomonie is at about 80%.
Most parts of southern Wisconsin are still at 50% or below, projected to hit peak in a week or two.
To produce the brightest, most intense fall colors, trees need a summer that’s not too hot or dry, and in the fall, sunny days and chilly, frost-free nights, the DNR said.
Leaves turn colors in autumn when trees get less sunlight and produce less chlorophyll, their natural green pigments. When trees finally stop producing chlorophyll, other yellow, orange and brown pigments start to show through in their leaves.
Red leaves come by way of a different pigment. Trees produce a different type of pigment to recover nutrients from the leaves before they fall off, according to the DNR. That pigment causes some trees, like maples and sumacs, to turn red, purple and crimson in the fall.
“The reds and purples are produced right after the chlorophyll breaks down, but it needs that cold weather,” Matula said. “Not freezing, but cold, to get those (colors) produced. Some of that color production is only in a few trees here and there, but not widespread.”
The Wisconsin Fall Color Report can be found at www.travelwisconsin.com/fall-color-report.