Dry winter weather stressing out trees in the Chicago area
CHICAGO (CBS) - More than three million people in Illinois experienced abnormally dry or moderate drought conditions in January 2025. That's a small piece of a bigger climate puzzle impacted by weather pattern swings over the past decade.
"In northern Illinois, we are seeing a decline in a lot of our native oak trees and this is really due to climate change," said Tom Tiddens who is an arborist with the Chicago Botanic Garden.
"I'm kind of a plant doctor in a way," he said describing his 30-year career. He now leads the Plant Health Care Department.
He and his colleagues have noticed significant changes with 100- and 200-year-old oak trees at the Chicago Botanic Garden, as well as in forested areas in the state over that time.
"The conditions they evolved with have changed so much, they're just not faring it very well," he said.
May 2020 notched the wettest May in 150 years in Chicago. That year also recorded one of the wettest springs. The warmest year on record was 2024, with an especially mild fall.
This was not good for the grand old oaks.
"Trees would like winter to come on nice and slowly, and then have a nice cold winter," said Tiddens, "and then also the inverse when we get into spring have it slowly come and get to the normal temps."
Big temperature and precipitation swings within a short time frame can also stress out plants, especially trees.
"What we're seeing are these big ups and downs. The past few years, it seems like December has been a very mild month, and then boom, all of a sudden, winter is here," Tiddens said.
On some of the 50-degree December days last year, he noticed flowers blooming.
"These plants that had to push out flowers in December, well, they're going to have to reenergize to regrow and put out flowers in the springtime," Tiddens said.
He said plants and trees have budgets, just like people. Tree budgets are made up of the resources used for growth or for defense.
"When they're under stress, they have to put all of their allocations for growth and their budget for defense drops down. So they're more susceptible to insect and disease problems," Tiddens said.
There is hope.
Oak seedlings sprouting at the Botanic Garden bring growing hope for the future.
"A lot of the researchers are feeling that new oak seedlings, when they come up, will evolve with the new weather conditions," said Tiddens.
Chicago's hardiness zone changed in 2013 from 5b to 6a. That allows people to try something new in their home gardens.
"When you do go to choose a plant, choose one that's appropriate for our conditions," Tiddens said. "Something nice and hardy."
