CHICAGO — If you’ve felt like there’s an unusual amount of fluffy cottonwood seeds floating through your windows, sticking to your skin and stuffing up your nose, you’re spot on.
This year, cottonwood trees are releasing more seeds than usual, according to Jalene LaMontagne, a biology researcher and professor at DePaul University.
It’s a phenomenon called mast seeding, which happens every few years when trees expel more seeds than they typically would because a variety of environmental conditions allow it, LaMontagne said.
The process usually only lasts a few weeks, but fluff has piled up this year because there hasn’t been as much rain to clear it out, LaMontagne said. This May was one of the driest recorded in city history.
While running with her dog in Irving Park, Cate Conroy turned the corner and “stopped in [her] tracks,” she said.
“I was stunned,” Conroy said. “It looked like it had snowed and the sidewalks had just been shoveled. When I got closer, I realized that it was all the cottonwood seeds. I’ve lived in the city for almost my whole life and I’ve never seen anything like this before.”
Brittany Sullivan, who has lived in Lakeview for about two years, said she also was stunned by the omnipresent fluff.
“I always pay attention to when cottonwood season pops up because I have really bad allergies, so I kind of knew it was coming because you look outside and it kind of seems like it will snow,” Sullivan said. “But I have never seen it pile up so badly on the sides of the road.”
A variety of trees experience mast seeding every few years, including maple trees and most conifer trees. The trees don’t have the resources to produce massive swaths of seeds every year, so they send out a big burst of seeds every few years, LaMontagne said.
It’s all part of trees’ efforts to ensure future generations of trees can grow, LaMontagne said. Even though each cottonwood seed is attached to a piece of fluff to enable it to travel far distances, the majority of the seeds will never take root, LaMontagne said.
“It has to do with this strategy trees have, they have to produce lots of seeds to make sure that other creatures don’t eat them all and they want the seeds to end up in a really good spot so that they can germinate and have the potential of becoming a tree,” LaMontagne said.
The cottonwood trees have actually been preparing to unleash this summer’s seed blizzard since last year, LaMontagne said.
Since last summer was warm and dry, the trees created more reproductive structures than they usually would, increasing the number of seeds they’re able to produce now, LaMontagne said.
More seeds paired with this year’s drier weather has resulted in the excessive swaths of cottonwood fluff blanketing the city, LaMontagne said.
Jennifer Schulze of Bucktown said she’s noticed tons of cottonwood seeds as well as lots of seeds from her block’s honey locusts, which are another mast-seeding tree.
“We have a lot of cottonwoods, but we have much more honey locusts,” Schulze said. “I’ve never seen anything like it. Last week, you’d be outside and think it was raining, but it was just these seeds pouring out of the trees. It’s definitely settled down this week, but my whole yard and deck and everything is still covered with it.”
Water is really one of the only reliable ways to remove the cottonwood seeds, LaMontagne said.
“I saw my neighbor out there with a leaf blower the other day, and almost as soon as he went inside, it was all back again,” Schulze said. “It’s everywhere. It’s on your lawn furniture, your stairs, your stoop, your deck. You wipe it off and it comes back an hour later. And it sticks to you, too. It’s all over my house, I can’t stop tracking it in.”
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