Heads up! Stressed-out trees are raining down acorns and nuts across Michigan

Sep 24, 2021
Originally published on September 24, 2021 2:12 pm

Have you been noticing more acorns and walnuts in your yard than usual this season?

It’s not just you, says Bert Cregg, a professor in the department of horticulture at Michigan State University.

“It's sort of a perfect storm, if you will,” Cregg said of the factors leading to this season’s “copious” mast—not a “crop”—of nuts.

“That's the term that foresters would use or people that deal—especially people that deal with wildlife management. They pay attention to, you know, how many acorns are being produced each year because that's obviously what's feeding a lot of our wildlife. So to talk about the mast year, this is a heavy mast year.”

As for what caused this year’s heavy mast, Cregg pointed to a number of conditions ranging from a tree’s level of stress to weather from last year.

“So, the nuts and things that you're seeing, those are from flowers that were produced early in the spring. Those flowers came from buds that were actually produced last year. So it's not so much the weather this year, although that has a role, but it's also the weather last year.

“And we did have a fairly stressful summer last year, especially the early part of the summer. And stress is one of the things that triggers trees to flower. It's sort of an evolutionary thing. If the tree is under stress and thinking, in quotes, that it's not going to be able to make it, then it's first thing is to try to reproduce.”

Cregg likened this habit to that of apple and cherry trees, something Michiganders may be quite familiar with.

“And if trees produce a lot of fruit one year, they'll produce less the next year. And if it's less one year, it'll be heavy the next year.”

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