The Oak Tree's Busy Season
After losing many of our oaks to oak wilt, I've come to appreciate every acorn a little more. Here's why these mighty trees are so important to Michigan's forests and wildlife.
Every fall, I find myself looking for acorns.
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Not because I need them, but because they remind me of what used to be here.
When we first moved to our property, mature oak trees were one of its defining features. They shaded the trails and each autumn covered the forest floor with acorns. Then oak wilt arrived. Over the past few years, we've watched tree after tree succumb to the disease. Some had to be removed for safety. Others simply stood a little thinner each season until they were gone.
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It's hard to lose trees that have likely stood for a century or more. Their absence changes more than the view. It changes the rhythm of the forest and the lives of the wildlife that depend on them.
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There are two main groups of oak trees in Michigan: red oaks and white oaks.The acorns of red oaks take two full years to mature. They remain on the tree through two growing seasons before dropping in autumn, lying dormant over winter, and germinating the following spring.​
White oak acorns mature in just one growing season. They fall in early autumn and often begin sprouting within days. Neither type produces the same number of acorns every year. Instead, oaks follow boom-and-bust cycles known as "mast years." Red oaks typically produce abundant acorn crops every three to four years, while white oaks have especially heavy crops every four to ten years.
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Those bumper years matter. Acorns feed more than 150 species of Michigan wildlife and are packed with fats, carbohydrates, and nutrients just when animals are preparing for winter. Yet very few ever become trees. Roughly 83 percent are eaten by wildlife, another 6 percent are consumed by insects such as acorn weevils, about 10 percent never fully develop, and less than one percent survive to sprout into the next generation of oaks.
Not all acorns are equally popular. White oak acorns contain fewer tannins, making them sweeter and easier to digest. Red oak acorns are more bitter, though they provide slightly more energy.​
White-tailed deer eagerly seek out white oak acorns, which can make up as much as three-quarters of their late fall and early winter diet. Gray squirrels usually eat white oak acorns immediately but tend to cache the more bitter red oak acorns for later. Wild turkeys scratch through the leaves in search of acorns, swallowing them whole before grinding them in their gizzards. Blue jays, woodpeckers, ducks, and many other birds also rely on this annual harvest.
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As I walk our woods today, I still notice the young oak seedlings pushing up through the leaf litter. Each one feels a little more precious than it once did. After seeing so many mature trees disappear, it's impossible not to root for the next generation. Every tiny acorn that escapes hungry mouths carries the possibility that, decades from now, someone else will stand beneath its branches and wonder how something so small could become the heart of a forest.
Black and White Warbler