Nature: Fall Really is Nuttier than Usual

By Tom Springer If you’ve recently noticed a bumper crop of acorns in your yard and driveway, then you’re not alone. Fall 2021 has turned out to be what biologists call a “heavy mast year.” That means a year when hardwood trees produce far more nuts (mast) than usual. There’s been a nutty surplus not only in the Kalamazoo area, but across the Midwest and the Northeast.

Especially on roads, it’s not hard to see where the nuts have fallen. For oaks and hickories, look for a whitish meal where the nuts have been fl attened by passing cars. For walnuts, it’s a greenish-black smear of the husks and nuts that tells the story. In the woods, at places such as the Source Pond and Beech Maple trails at KNC, look for stumps where a squirrel or chipmunk has lately enjoyed an acorn or beech nut breakfast. Their nibbled remains remind me of toast crumbs on a kitchen table.

When people think of tree fruits, it’s usually apples, cherries and peaches that come to mind. Yet nuts are the fruits that hardwood trees produce and they do so from fl owers, just as trees in an apple orchard do. Except that instead of individual blooms, the fl owers that appear on nut trees are known as catkins. They grow in graceful cylinders, somewhat like yellowgreen icicles. In May and June, you can see shed catkins, brown and stringy, laying where they’ve fallen from the nut trees above.

So why the abundance of catkins and nuts this year? Biologists say there’s two likely reasons. First, the 2020 drought prompted nut trees to create more fl ower buds than usual. Second, the 2020-2021 winter was mild, followed by a largely frost-free spring. These combined factors made ideal fl owering conditions for nut trees.

“If a tree is under stress and thinking that it’s ‘not going to make it,’ its fi rst thing is to try to reproduce,” said Bert Cregg, a Michigan State University horticulture professor, in an interview with Michigan Radio. “And that’s why we get this stressed fl ower, if you will, that occurs this year even though the stress was last year.” Hardwood trees expend considerable energy to produce a heavy mast crop, which helps explain why they only do so every fi ve to 10 years. In fact, producing too many nuts on a regular basis may actually hamper tree survival. During heavy mast years, animals such as deer, rabbits, squirrels and turkeys all enjoy a high-calorie feeding binge. Consequently, with larger stores of fat, they’re more likely to survive the winter and produce their own bumper crop of offspring the next year. In the circular ways of nature, that brings more deer and rabbits that also like to browse on tender tree seedlings. Long term, too much nibbling can wipe out the next generation of hardwood trees. The one exception here is squirrels. They bury caches of acorns throughout the forest, and more than a few of these will sprout into trees. This Thanksgiving, as the nuts rain down on trails and windshields alike, let’s embrace the heavy mast year for what it brings: a rare gift of natural abundance to profi t all creatures that call the forest home. Tom Springer is grants manager at the Kalamazoo Nature Center and author of “The Star in the Sycamore” and “Looking for Hickories.”