Staff at the Morton Arboretum near Chicago say heavy rainfall early this year followed by a drier-than-normal spring has the trees producing large numbers of the nuts, technically called fruits, the Chicago Sun Times reported Thursday.
"It's a natural overabundance of acorns in certain years that we believe helps the trees beat their predators that feed on acorns," Kris Bachtell, vice president of collections and facilities at the arboretum, said.
Squirrels, raccoons, coyote and deer feed on the nuts, but people have also used them as food.
Native American tribes made a sort of high-calorie "tofu" from acorns to get them through winter months, Bachtell said.
There's usually a heavy crop of acorns every over year, and this year was schedule to be a heavy year boosted by the weather, Boyce Tankersley of the Chicago Botanic Gardens said.