One way oak trees react to stress is by producing a lot of acorns. They’ve had a lot of stress this summer. Ben McCanna/Staff Photographer

It has been a tough year for oaks and apples. And the tree species, surprisingly, at least to me, act in almost opposite ways in reacting to the stress.

Let’s start with oaks, which regular readers of this column probably know by now are entomologist/conservationist Doug Tallamy’s favorite tree because they support more than 500 species of caterpillars (more than any other plant) and at least 3,000 other species in the animal kingdom.

In late August, just as I was waking up each morning, acorns started clunking as they fell on the roof of our house. Soon the driveway and patio were covered. It’s a mast year for acorns, meaning there are a lot of them. Aaron Bergdahl, a forest pathologist with the Maine Forest Service, said the heavy mast years occur about once every five years.

“They are the result of a complex set of factors that we may never fully understand,” he said.

But scientists generally agree that mast years are triggered by tree stress. The trees produce more seeds than usual as a way to ensure a lot of baby oaks should the parent oak succumb to pests or disease.

Part of the stress on Maine oaks is from destructive insects, including browntail moth, winter moth and spongy moth (which used to be known as gypsy moth). Winter moth isn’t as bad now as it was five or six years ago but is still around. Browntail moth has been a big problem in part of the state for the past decade or so. Spongy moth has been around for many decades but is on an upswing. The wetter-than-normal summer has only added to the problem.


A result of the extra acorns is that rodents will have plenty of food this winter. Squirrels and chipmunks, for two, will likely have a boom in population next year. Unfortunately, it will likely also mean more road kill next summer. Squirrels escape predators by running in a zig-zag pattern, as you have probably noticed when you drive. This is an excellent strategy if their predator is a hawk, not so much if it’s a speeding car. The population boom that results from plentiful food this year means more squirrels out and about crossing roads looking for food next year. (Drivers, slow down!)

Most gardeners will want to remove as many acorns as they can. Yes, oaks are wonderful, but we’ve enough on our property and would rather not spend a lot of time pulling oak seedlings out of our vegetable and flower beds next year. So far this year, I’ve swept up and raked 20 five-gallon pails of acorns and taken them to the town composting facility. I could compost them at home, with our leaves, but without enough grass clippings to create heat in the compost, they would take too long to decompose.

A friend showed me an interesting alternative to raking, a nut gather with flexible metal ribs that can be rolled along the lawn to pick up acorns, as well as apples, according to some pictures. She bought it at Drillen Ace Hardware in South Portland, but I’ve also seen them online.

Now on to apples.

All fruit trees, not just apples, had a tough year, said Renae Moran, a tree fruit specialist with the University of Maine Cooperative Extension. Very cold temperatures in February killed the buds on peach, plum and sweet cherry trees. (Our peach tree never even produced leaves, so we removed it.)

Then a freeze on May 18 reduced the apple crop in parts of the state.


“Apples with nonlethal injury have frost-bitten skin and some have internal browning,” Moran said. “Most, however, are in good shape.”

She said frequent rainfall has increased the incidence of disease, with sooty blotch and flyspeck, both fungal diseases, found in every orchard, as well as scab in susceptible varieties.

Bergdahl summed it up nicely: “The very wet weather has been both a tree stressor and has also driven the multiple infection cycles of the fungal leaf pathogens leading to heavy disease loads, triggering premature defoliation.”

We’ve noticed that ourselves. Last year, our (unnamed) seedling apple tree produced a good crop. But this year, it lost its leaves early and we got only a couple of sick-looking apples. I do hope it survives. The Red Astrachan apple that we planted as a seedling last year looks healthy, though.

And that’s a bit of good news to lift my spirits while I rake acorns and shovel them into five-gallon pails.

Tom Atwell is a freelance writer gardening in Cape Elizabeth. He can be contacted at:

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