THE LEAFLET

If you’ve heard (or felt!) the unmistakable sound of an acorn falling from tree more than usual this year, you’re not alone. This year is a special, and prolific, one for the region’s oak trees as John Kelly reports in the Washington Post:  

“‘You’re witnessing one of nature’s weirdest phenomena that we still don’t fully understand.’

And that’s exactly what Scott Aker said the other day when I rang him up at the National Arboretum, where he is the head of horticulture and education.

Aker confirmed that I was not imagining things. There really are a lot more acorns raining down from above this fall.

‘We’re seeing a lot of white oaks now producing a bumper crop of seeds,’ he said. It’s called a mast year.

As for why . . .

‘It’s called the predator satiation hypothesis’ said Michael Steele, a biology professor at Wilkes University in Pennsylvania. Lots of things like to eat acorns, including squirrels, which eat them from the outside, and weevils, which eat them from the inside.

Every few years, trees such as oaks produce an overabundance of acorns, so many that the predators can’t possibly eat them all. Squirrels and jays carry them away from under the parent trees and bury them, but many acorns are never found again.

Elizabeth Crone, who teaches ecology and statistics at Tufts University in Massachusetts, said masting ‘is synchronized over the scale of hundreds of kilometers but it is not countrywide.’ Northern New England — Maine, New Hampshire, Vermont — had an oak mast last year, but it is experiencing a paucity of acorns this year.

Heavy acorn production takes a lot out of a tree, so most can’t do it every year. Scientists aren’t sure how they know to do it the same year. It’s probably related to spring weather, Crone said. A wet spring or a late spring frost curtails pollination for that year, setting the table for a mast the following year.

One thing is for sure – we’ve definitely had a wet year. Since last year was New England’s mast year and we’re in the throws of one this year, watch out Southeastern oaks – you could be next.