A squirrel gathers acorns Friday in a yard in Saco that’s covered with them. Shawn Patrick Ouellette/Staff Photographer

It’s “raining” acorns across Maine, pounding rooftops and pummeling decks, and the state’s worsening drought is likely to blame.

At Felicia Knight’s home in Scarborough, several oaks have put out so many acorns, she sweeps her deck and walkways regularly to make sure no one falls. Lawn care workers used leaf blowers and shovels to remove a large pile of acorns last week and they’ll likely have to do it again soon.

“They’re cascading down,” Knight said. “It sounds like someone’s shaking the trees and it’s raining acorns. It’s like walking across ball bearings in the front yard.”

Widespread reports of oaks dropping their fruit early and in large amounts come one year after a heavy acorn mast, or crop, in 2019. Heavy masting typically occurs every two to three years, and other trees may suffer through the winter if they don’t get more water this fall.

While some acorns falling now are brown, ripe and fully formed, others are smaller, green and underdeveloped. The latter indicates many oaks are stressed following a dry summer that has caused moderate to extreme drought conditions across Maine.

“It is very strange for an oak tree to have a heavy mast year in two consecutive years,” said Aaron Bergdahl, a tree pathologist with the Maine Forest Service.

Bergdahl said oaks usually synchronize heavy mast years, when trees across a wide area put out large numbers of acorns in the same season. Exactly how they coordinate this reproductive response is unknown. A large oak can drop as many as 10,000 acorns to ensure reproduction beyond those eaten by deer, squirrels and other animals or destroyed by disease and insects.

Beneath the oak in Berghahl’s backyard in Manchester, the fallen acorns are smaller than usual this year and still a bit green, indicating that they’re not quite ripe.

“It’s likely a stress response,” Bergdahl said. “It takes a lot of energy to produce acorns. When there are added stressors like this drought, a tree may not be able to put additional energy into growing acorns to maturity.”

Oaks may respond with earlier and heavier masting, Bergdahl said.

Knight posted a photo of her bumper acorn crop on her Facebook page, drawing sympathetic comments from friends throughout Maine. Some predicted a squirrel population explosion next year. Most declined her offer to share.

“I don’t even know where to begin to pick up all the ones that are on the ground in my yard!” wrote Jennifer Burke of Biddeford.

In Brunswick, the three oaks in Becky Smith’s yard started dropping acorns weeks ago. She and her husband collected a trash can full before they had a new lawn seeded over a week ago. Now, the lawn is covered with acorns again.

“If the new lawn does not take, we are going to grow an oak forest,” Smith wrote on Knight’s Facebook post.

“They just keep falling and they sound like gunshots when they hit the deck,” Smith said. “I contacted a local pig farmer to see if he wanted them because acorns are supposed to be good for pigs, but he doesn’t have pigs this year.”

The Smiths can’t walk on their new lawn for a couple more weeks. Undaunted, Smith’s husband has managed to fill another trash can, using a rake to carefully roll all the acorns he can reach from the perimeter of their yard.

“It makes him feel better, I think,” Smith said.

On the upside, the drought may produce earlier, more vibrant colors in some areas during foliage season, Bergdahl said. But it also may result in tree loss through the coming winter and reduce growing, budding and blooming into next spring.

To combat this, Bergdahl suggested that property owners provide additional water to trees and shrubs through October, if possible. A few gallons each week will help stave off winter burn in evergreens and promote root growth and bud development that continues after leaves fall.

“Supplemental watering is definitely a good idea,” Bergdahl said.

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