More Acorns Than Usual Are Falling This Year, And It’s Driving People Nuts

Neighborhood social media groups are rife with questions about this year’s “acorn apocalypse,” the wisdom of wearing a hard hat or helmet during an autumn walk, and even who’s responsible if an acorn dimples a car parked under an oak tree.

Short answer on the latter: Let the insurance companies sort it out.

It’s a “mast year” for certain species of oak trees, which means they’re raining — hailing might be a better term — acorns at a furious pace. One large oak tree can drop up to 10,000 acorns in a mast year — or between 10 and 15 bushel baskets full — depending on the tree species.

In botany, the term “mast,” which comes from the old English “mæst,” describes the phenomena of the boom-and-bust synchronized reproduction of nut- and fruit-bearing trees. Boom times — or mast years — occur every two to five years, with smaller acorn crops in between.

It’s not just a few trees here and there, either. A red oak tree in the forests of Upstate New York would hurl an abundance of acorns to the ground at the same time as red oak tree on the streets of Chicago.

There are about 90 oak species in North America, and they all have different reproduction cycles. Red oaks, white oaks, chestnut oaks and bur oaks all are experiencing a mast year, according to multiple reports.

Are Trees Talking?

Scientists don’t know exactly what’s going on.

But here’s what’s not going on: Mast years are not a harbinger of severe winter. That’s just more folklore foolishness, like the misguided notion that woolly bears and persimmons are weather prognosticators.

The phenomena, which has been casually described as “a time when the oak trees conspire among themselves and go all out in a nonstop orgy of acorn production,” is enduringly fascinating and even mysterious to scientists.

The synchronized reproduction event could be triggered by environmental conditions or pollen availability, but scientists don’t think annual rainfall and temperature fluctuations alone account for the abundance of nuts in mast years.

Another theory surrounds chemical signaling, a “conversation” of sorts between organisms, in which trees use chemical molecules to send messages internally and to other organisms, helping them respond to threats, grow, and interact with their environment.

“My own hypothesis about oak population dynamics is that this group of trees co-evolved with a certain herbivore that loves to eat acorns, stashes the acorns in hidey-holes all over the place, and has a very short life expectancy: the squirrel,” Chris Best, Texas state botanist for the U.S. Fish and Wildlife Service, told the San Antonio Report.

“Every squirrel that gets eaten by a hawk or coyote leaves scads of stashed, uneaten acorns, some of which germinate to become new trees,” he said.

Whatever the reason, the cyclical nature of acorn production may have an evolutionary benefit to oak trees, according to the New York Botanical Garden.

As the theory goes, years of lean acorn production have reduced the populations of predators such as chipmunks, squirrels, turkeys, blue jays, deer and bear. They can’t forage the abundance of nuts that fall in a mast year, which leaves enough behind to sprout into future oak trees.

The consequences of mast years could be felt for years to come. More deer may be attracted by an easy food source, and that could mean more ticks and tick-borne illnesses, such as Lyme disease.

Are They Edible?

Human foragers who view acorns as a “superfood” that can fight diabetes and obesity are giving squirrels some competition for acorns, according to an article several years ago in The Wall Street Journal titled “Humans Are Gobbling Up Acorns, Driving Squirrels Nuts.”

The article noted that surge in human foraging in South Korea for acorn noodles, jelly and powder left significantly fewer acorns on the ground, causing the squirrel population to dwindle.

Acorns are edible and even tasty, but not in their raw form and not without a lot of work. They contain tannins that can be toxic to humans and have a bitter, unpleasant taste.

Leaching the nuts — that is, repeatedly soaking them in water — removes most of the tannins and makes them safe, but also adds a nutty, sweetish flavor.

Nuts may be leached using either a cold water or hot water method. They can be prepared in a variety of way whether roasted and candied for a snack, added to soups and stews, or served as a side for grilled fish, chicken and meat. They can also be ground into meal or flour, or used as a coffee substitute.

For the latter, the tannins are removed, and the nuts are roasted, then ground up to steep in hot water. The resulting beverage is a caffeine-free, dark brew with a nutty flavor that is distinct from traditional coffee.

Acorns can be extremely toxic to livestock and some pets. A horse owner posted on Instagram about the five-hour job of raking acorns, so the horses wouldn’t be “tempted” to eat them. The tannins in acorns are toxic to horses, cattle and sheep, as well as other livestock.

It’s ‘Like Walking On Marbles’

There’s no question mast years are annoying for people who don’t want to eat acorns or simply admire the elegant reproductive strategy of oak trees.

Falling acorns can cause a range of injuries, ranging from bumps on the head and chipped teeth to sprained ankles and other injuries from falls when they collect like so many ball bearings or, as several people have noted in recent social media posts, marbles.

“It’s like walking on marbles, like walking on ice, or worse,” one person said in a public Facebook post after encountering a pile of acorns on a recreational trail in a Midwest city. “Please be careful, everyone.”

“Acorns everywhere,” someone else said in a post on X. “Walking across the yard is like walking on marbles.”

“More walking alerts!” another person said on Facebook. “I’ve never seen so many acorns. It was like walking on marbles.”

Sweeping or blowing acorns into a pile is one way to clear smaller areas like sidewalks and driveways to eliminate fall and tripping hazards.

“Use a shop vac, with just two solid hose extensions and nothing on the end,” one person advised on Facebook. “This is a task that your kids can even do. It’s actually very simple and quick, fun way to pick them up. The sound of the acorns hitting the bottom of the canister is very satisfying. I’ll never pick them up any other way.”

Many communities have reforestation programs that will collect acorns to grow new oak trees. Homeowners may also choose to grow saplings to plant in their own yards. Or, they can be disposed of with other yard waste in most cities.

Deputy Opened Fire After Acorn Fell

Depending on what they land on, falling acorns can cause a symphony of sounds, ranging from “thuds” and “bangs” on roofs and patios to “pops” on harder surfaces that can sound more threatening.

In 2023, a Florida sheriff's deputy mistook the sound of an acorn falling on a patrol vehicle for gunfire and opened fire on a suspect in the back seat, who had already been searched and handcuffed.

Body cam video showed the deputy yelling “shots fired!” multiple times as he fell to the ground and repeatedly fired into the patrol vehicle. A second officer also fired into the vehicle. The suspect was unharmed, and the officer who mistook the sound resigned after an internal affairs investigation, NBC News reported.

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Editor’s note: This article has been corrected to reflect that a tree can shed 10,000 acorns in a mast year, enough to fill 10 or 15 bushel baskets.