More seeds from Iowa’s silver maples signals trees may be drought stressed

Seeds, samaras, helicopters: Whatever you call maple seeds, there is a bumper crop this spring in Iowa.

Iowa’s silver maples and silver maple hybrids produced a surplus of seeds this year, likely as a response to several years of drought, said Mark Vitosh, Iowa Department of Natural Resources district forester covering seven Eastern Iowa counties including Linn and Johnson.

“The fact we've had three to four years of drought is probably why we had a bigger flower crop this year and bigger seed crop,” Vitosh said. “If a tree is severely stressed, it tends to put energy into those flowers. It's a defense mechanism.”

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Years when trees outdo themselves with seed production are called “mast years” because mast is the accumulation of seeds and nuts on the ground. Maple seeds feed squirrels, chipmunks, finches and turkeys, among other wildlife.

Maples have mast years every three to five years, said Jeffery Iles, an Iowa State University horticulture professor, in a post online for ISU Extension.

The species having a moment this spring are silver maples (Acer saccharinum), red maples (Acer rubrum) and hybrid red x silver maples (Acer x freemanii), Iles said. The seeds are pink or red at first, which can change the overall appearance of some maples before the seeds fall.

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The production of seeds also takes some energy away from leaf production, so maple trees may have smaller leaves than they usually do this time of year, Iles said. The trees should recover their leaf growth later in the summer, he said.

Whether the abundant maple seeds are good or bad depends on where you live.

“In urban areas, people may observe them (seeds) in their gardens,” Vitosh said. “My neighbor just despises them because they make a mess in his downspouts and garden.”

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The best non-chemical way to deal with the seeds in your yard is to pull them out before they become established, he said.

But in Iowa’s river bottom woodlands, silver maple is a key species that is fast growing and provides food and shelter for wildlife. Woodland owners looking to regenerate bare areas may benefit from the showers of spinning seeds that fall on bare soil and germinate into saplings, Vitosh said.

But a mast year also can be a sign of stress on trees in your yard or woodland.

“A couple weeks ago, a lot of places got 2 to 3 inches (of rain),” Vitosh said. “But if you go out and look at things, it's stinkin' dry. This seed production is a little bit of an indication something is going on.”

Iowa has endured several dry years with occasional heavy rains providing only temporary reprieve. The U.S. Drought Monitor showed about two-thirds of Iowa was abnormally dry or in moderate drought May 15 after below-normal rainfall in April.

Tree owners should look at their silver maples and see if they are producing more seeds and watch for other signs of distress, Vitosh said. If you don’t have many trees, you may be able to water them during periods of drought. The best way to do this is to water once a week for four to eight hours under a tree’s canopy.

“There's not anything we can do about that in a woodland situation,” Vitosh said. “We need to continue to watch those things to monitor the overall health of our woodlands.”