Michigan is well-known for its deciduous trees and their red, orange and yellow hues in the fall months, and mid-Michigan starts to see peak colors in mid-to-late October.
The change in color is triggered by cooling temperatures and shortening daylength, as well as increasing soil moisture.
While the El Niño will have no impact on daylength, it is expected to bring warmer temperatures and below-average rainfall to the state this fall, leaving some wondering when the trees will change colors.
According to Bert Cregg, a Michigan State University professor of horticulture and forestry, the leaves will most likely change colors on schedule.
The trees typically start to change color in the Upper Peninsula in early October before moving their way down the state week by week. Cregg said that the next three weeks have “equal chances of being warmer or cooler,” so temperature won’t affect the color schedule.
“Everything that we can look at would say we're looking at probably a pretty average fall color year,” Cregg said. “I think we're kind of going in the fall the way we want to. The recipe, you know, ‘Dr. Craig, what would be the best scenario for our fall color?’ It's kind of what we're setting up."
Cregg is an MSU Extension specialist with an extensive background in tree physiology. He said soil moisture was a "wild card” in determining when the leaves will change color.
“We’re kind of wet up north, which is, for people who want to go north looking for leaf color, kind of good,” he said. “It should keep the leaves on the trees longer and probably will not be promoting an early fall color that way. And then the lower third or so of the state is relatively wetter. There's kind of a band, from maybe Muskegon over to Saginaw Bay, and a county or two either side of that line that is dry.”
Dry soil can cause leaves to change color and drop ahead of schedule due to stress.
If any trees are to be impacted by the El Niño, Cregg said it's most likely to be Christmas trees, specifically concolor firs.
“The Christmas tree folks will talk about needle set, and what we're talking about there is certain species are really cued into having some cold exposure,” he said. “It really helps them to maintain their needles after they're harvested, so when once you cut your tree and bring it in the house, having a tree that's had some cold exposure really helps for some of those species."
Species like concolor firs rely on an early winter cold to help mitigate shedding once the tree is brought indoors. The El Niño, which is forecasted to bring warmer temperatures and less snow to Michigan this winter, could impact that.