Why there is a bounty of acorns this season: ‘Oaks are having a moment’

Acorns on the ground at the Fabyan Forest Preserve in Geneva. Oak trees are producing large numbers of acorns this year.

It’s not your imagination. Oak trees are producing huge numbers of acorns that are crunching underfoot and snapping like popcorn when driven over.

Stand under an oak tree for awhile and you may get bonked as an unpredictable fall phenomenon continues.

The bumper crop is called a “mast” – when oak trees periodically produce more acorns than can be eaten by squirrels, mice, chipmunks and other critters.

Welcome to October, designated in 2015 as OAKtober: Oak Awareness Month in Illinois.

The term “masting” originated centuries ago and refers to nuts of forest trees, such as acorns, accumulated on the ground.

Experts say mast year triggers are not well understood but the occurrence generally is accepted as nature’s way of ensuring oaks will carry on.

“It’s just a reproductive strategy of trees. Oaks are having a moment,” said Jessica Turner-Skoff, science communication leader at the Morton Arboretum in Lisle.

Many animals eat acorns and several hoard or cache them, dispersing them across the landscape, explained Matt Ueltzen, manager of restoration ecology for the Lake County Forest Preserve District.

If oaks produced a stable amount of acorns each year, the number of critters that eat them would increase to match the output and there wouldn’t be any acorns to germinate into new trees, Ueltzen said.

The sun breaks through the foliage at Tyler Creek Forest Preserve in Elgin. Oak trees are producing a bumper crop of acorns this year.

“When masting occurs, there are not enough seed predators to consume all that are produced, ensuring survival and dispersal of the excess acorns that cannot be eaten,” he said.

If acorns were produced only during mast years and not in other years, the number of animals to disperse them likely couldn’t be sustained, Ueltzen said.

So masting could be an ecological strategy or adaptation to keep those critters at moderate levels most years and stuff them during mast years so oaks survive, he added.

Libertyville resident Mike Graham said he planted 29 bur oaks in his backyard two decades ago.

“I have the fattest squirrels in Lake County,” said Graham, vice president of operations for Landscape Concepts Management in Grayslake.

Both red and white oaks – the two major groups in Illinois – mast but on different cycles: two to five years for white oak and five to seven years for red oak, according to Turner-Skoff.

Acorns from red oaks were pollinated in spring 2022, she said.

White oaks produce acorns much faster and those falling now were wind-pollinated this past spring.

Sometimes the cycles overlap.

“It would appear that this fall we are experiencing synchronicity between several species, leading to the large volume of acorns everywhere,” Ueltzen said.

“It’s one of the great examples of how we don’t know how our world works,” added Turner-Skoff.

Oak trees are dropping an abundance of acorns this year that crunch underfoot and snap when driven over.

How trees “coordinate” masting is a mystery, although favorable weather without extremes, especially in spring when oaks are flowering, likely is related, Ueltzen said.

But don’t read too much into it.

“Masting does not predict the weather,” he said. There are tales that masting relates to or will be followed by a severe winter, but that’s not the case, he added.

Masting can have implications down the road for “predator-prey dynamics,” according to Turner-Skoff. For example, research has shown an increase in the population of small mammals due to masting can lead to an increase in ticks and, ultimately, the prevalence of Lyme disease two years into the future.

But because nature – and masting – can be complicated, it is hard to make concrete predictions, she added.

“It’s a great excuse to get outside, interact with nature and see what animals are eating your acorns,” she said.

Despite the bounty, oaks need help. As a keystone species, they create the framework of the ecosystem on which many species depend, Ueltzen said, and if oaks disappear – so will many plants and animals.

Since the 1830s, 88% of oak-dominated communities in Lake County have been lost. Remaining oaks are not regenerating as they should because they are being shaded out by invasive buckthorn or honeysuckle as well as cottonwood, maple and elm trees, Ueltzen said.

Many of the largest oaks are nearing the end of their life spans and extreme weather is hastening their decline, he added.

“If you have oaks on your property, consider what you can do to support them,” Ueltzen said.

Mick Zawislak - Daily Herald Media Group

Mick Zawislak has covered Lake County for the Daily Herald since 2002