The kids have started school, the State Fair is nearly over, and it’s getting to feel like fall. Every day, dusk inches up, a minute here, a minute there. There’s a nip in the morning air, and already, leaves are showing signs of turning bright colors before the wind shakes them loose and they flutter to the ground.
The autumn colors are a little early in getting their start this year, but the news isn’t all bad. Word on the street from fall color predictors is it’s likely to be a great fall for leaf peeping.
To understand why, a brief review of the changes trees undergo in the fall:
Leaves change color as photosynthesis, the process that trees and other plants use to feed themselves using sunlight, winds down, said Matthew Russell, a professor in the Forest Resources Department at the University of Minnesota.
Leaves start to change color when the days start getting shorter, in response to trees having less light to convert to nourishment. As the days get shorter, production of chlorophyll, a green pigment that allows plants to create energy from light, slows down. In the absence of chlorophyll, other pigments — anthocyanins, which produce red and brownish colors, and carotenoids, which make yellow and orange pigments — are visible in the leaves, Russell said.
Moisture can also help determine when leaves start changing. In dry years, leaves turn earlier because trees are distressed.
The weather we’ve been having lately can make those colors appear far more intense.
“These next couple weeks … if we continue to have some of these warm days, into the 70s, but very cool nights into the 40s, that can help to bring more color out as well,” Russell said.
Warm days produce lots of sugars in the leaves, and cold nights stop them from flowing out, which make for good anthocyanin conditions, or a year of brilliant red leaves, according to the U.S. Forest Service.
Peak fall colors are expected to be on display mid-to-late September in Minnesota, depending on the part of the state.
A fall color map built by a data scientist for SmokyMountains.com, a vacation rental company, attempts to predict where the best colors will be, when, based on historical and predicted temperatures and precipitation, past leaf peak trends and observation trends (Russell said the map looks accurate where Minnesota is concerned).
How things are looking at Minnesota parks
Minnesota park employees are already starting to see the leaves change color.
Up at Tettegouche State Park on the North Shore, “Most of the trees are still green, but the red maples and the sugar maples, a lot of them have started to turn. There’s lots of little highlights of red here and there,” said Kurt Mead, Tettegouche’s interpretive naturalist. Aspens and birches are starting to develop a noticeably yellow tint. Possibly, he said, the early start could be due to cooler temperatures.
If you want to see fall colors at Tettegouche, the peak is typically around the third to fourth week of September, he said. If you go, don’t forget to look down below the tree canopy.
“The asters, which are typically purple, peak in the fall,” Mead said. “They tend to get overlooked, poor things, because the leaves are so colorful. If you were to just look down every once in awhile, you’d see that there are wildflowers.”
At Blue Mounds State Park in Southwestern Minnesota, some of the oaks and plums have started to change color already — likely due to drought conditions that persisted for much of the summer, though there’s been more rain in the last month, said Chris Ingebretsen, park manager. Some geese are starting to fly out, too.
At Blue Mounds, though, perhaps the most spectacular fall sight are the prairie grasses, Ingebretsen said.
“Big bluestem and Indian grass will turn kind of a golden reddish tint, usually mid-September .. through the middle of October, even,” he said. “The grasses are phenomenal.”
For current leaf color conditions, consult the Minnesota Department of Natural Resources’ fall color finder.