Fall colors are already starting to emerge in the Red River Valley, but most Minnesotans are a month or more from peak leaf color this year.
The Minnesota Department of Natural Resources gave a pre-season briefing on the annual autumn show on Thursday, noting that for some colors — the yellows, oranges and browns —depend largely on the amount of daylight trees get. As the energy diminishes, green chlorophyll fades and reveals underlying leaf colors.
That is inevitable, as the planet turns around the sun and the days get shorter in the fall.
Other colors — the brilliant reds, pinks and purples — are more a function of weather, according to DNR forest health specialist Brian Schwingle. He says those colors depend on pigments known as anthocyanins.
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“They're produced in some, not all but some tree species in late summer and fall, especially when days are warm and sunny and nights are cool but not freezing,” Schwingle says. “The weather and a tree's crown exposure to the sun really affect how much red is made.”
So, stay tuned.
There already have been some signs: September started off with record heat, and as of Thursday, parts of the state have now slipped into exceptional drought.
Wildfire smoke may also play a role: soybean farmers already say the diminished light from this summer’s smoky haze has diminished crop yields, and it could impact trees as well.
With Minnesota slipping into a fourth year of below normal precipitation, and another year of real drought, it's still unclear what that means for fall.
“The good news I guess is that we haven't seen any obvious effect on our fall colors in recent years,” Schwingle said. “Maybe the brilliance of fall colors diminished across the landscape, but not at a level that most people would notice.”
The drier climate is having a lethal impact on a significant number of oak trees across the state, Schwingle noted.
“Over time, we’ve seen big changes in fall, as our climate in Minnesota has changed,” said Kenny Blumenfeld, senior climatologist with the DNR. “September's rapidly warming. That's basically the third fastest month for warming in Minnesota. October is a little bit of a break from that. But then November is also warming pretty quickly too.”
The DNR says it has a network of observers offering weekly updates — usually on Wednesdays — that will be used to compile its weekly color map, available here.
The peak colors will likely be along the Canadian border starting in a couple weeks, progress down the North Shore and around Bemidji through in mid-September, hit central Minnesota in late September and the Twin Cities by mid-October, wrapping up in about six weeks along the Iowa border.
The DNR says the best way to see them is to get outside, in some of the hundreds of state properties that are open to all this fall.
“We have 75 state parks and recreation areas. We have 59 state forests. We have 27 state trails, that's 1,300 miles of trails people can explore,” says DNR spokesperson Sara Berhow. “We have over 160 scientific and natural areas, really a lot of good places to get outside and there's really something for everyone.”