Formally, they're known as samaras; informally, as helicopters. In any case the spring of 2023 saw an abundance of deep pink maple seeds on Western Michigan University's campus.
Why so many? And why the unusually vivid color?
According to WMU biologist Todd Barkman, bright colors in flowers attract pollinators, and bright colors in fruits help animals to find them and disperse the seeds. But the wind spreads maple seeds, so the plant doesn't need to make them attractive to animals.
“Why would a red maple make a red fruit?" he asked. "It’s not like the wind is going to find it because it's more colorful. And so, there's got to be some other reason red maple fruits are red.”
A big year for buds
Flowering trees and shrubs tend to set lots of buds one year, and fewer the next. As it happens, this was a heavy year.
On top of that, in the southern half of the Lower Peninsula, the weather in early 2023 was kind to buds. The region had a mild winter, with no late spring frost that might have killed them off. That led flowering trees and shrubs to produce more flowers, which in turn, produced more seeds.
Is this likely to happen more often as the climate gets warmer?
“It really gets harder to predict other than to say it's probably going to become more extreme," said Bert Cregg, from the Michigan State University Extension and a professor in MSU’s departments of horticulture and forestry.
"Maybe we'll see more springs like this and then springs where we have nothing. So, it's maybe more a feast or famine kind of thing."
Cregg said next year will be lighter on flowers if trees and shrubs follow their usual pattern. But he added that the drought southwest Michigan is now experiencing could stress them into setting extra buds, in an effort to survive.
The April sun
Kalamazoo had an unseasonably hot April; temperatures rose into the 80s for four straight days in the middle of the month. With the high temperatures came an unusual amount of sunlight.
“It's very likely that the red maple fruits are reddish to protect them from UV damage," Barkman said.
That's because red pigments can help protect against the sun's rays. By producing pinker seeds, a maple tree could potentially increase those seeds' robustness and thus their chances of becoming healthy maple trees.
Barkman added that it’s possible we’ll see more brightly colored seeds as the climate warms.
“If we do have reliably more sunlight, more intense, sunny days during fruit production, at least for red maples, then yes, certainly, I think you'll see some more brilliant pinks, maybe more than you're used to seeing in the past.”
