Minnesota's oak trees are going squirrelly with acorn production

If the squirrels seem happier than usual these days, it's because this has been a bumper year for acorns.

We're not talking about just a few extra of the hard, woody capsules. The oak trees are literally going nuts, with some of them producing up to 10 times their normal output.

A large, healthy oak tree can produce as many as 10,000 acorns, so it's clear why there's a lot of those kernels piling up on lawns and sidewalks.

But forget the old wives' tale about Mother Nature helping the squirrels stockpile food because we're heading into a long, brutal winter. Granted, we very well might be heading into a long, brutal winter, but it's because we live in Minnesota. It has nothing to do with the acorns.

"I don't think trees can predict the weather," said Angela Gupta, a forestry expert for University of Minnesota Extension. Instead, "they react to it."

What they're reacting to is that we had a very good spring and summer for oak trees, she said.

But there's more to the story than that. Timing also plays a role. The production of acorns is cyclical, with a larger-than-usual crop turning up every two to five years.

"It's called masting," Gupta said. And without masting years, oak trees likely would die out.

"There are lots of animals that eat acorns," she said. If a tree produced the same number of acorns every year, the animal population would grow to match the food supply "and all the acorns would be eaten. By producing a bumper crop, a tree is producing more acorns than can be eaten and ensuring that some of them will survive to germinate new trees."

One of the fascinating things about masting, Gupta said, is that it happens in unison.

"We don't know how the trees know to do it" at the same time, she said. Some trees, such as aspens, share root systems that make it understandable that they would all react similarly.

"But oaks are individuals. How do all the red oaks, for instance, know to do this at the same time? We suspect that it has something to do with [conditions in the] spring, but we don't know for sure."

So let's move on to the next question: What does a homeowner do with all those extra acorns?

You can plant them, but Gupta warned that the success rate of do-it-yourself urban oak tree repopulation is not very high.

Squirrels often dig up the planted acorns, and any acorns that do manage to germinate need to be protected right away or they will become lunch for rabbits and rodents. Oaks also are slower growing than many other species, which can frustrate landscapers looking for quick rewards for their labor.

"It can work," she said of growing the trees, "but it takes patience."

If you do want to try it, make sure nut weevils haven't damaged the acorns. Put them in water; if they float, discard them — something has eaten the nut's innards. If they sink, they're good to plant. (Don't even bother to test acorns that are soft and mushy; they're starting to rot.)

University of Minnesota Extension recommends planting acorns 1 to 2 inches deep in spots several feet wide, with three to four acorns to a spot.

Oh, and plant them where you want the tree to grow.

"Oaks put a lot of energy the first few years into developing their root system," Gupta said. "Even though the seedling might be small, the roots can be fairly deep, which can make transplanting them tricky."

If you don't want to plant the acorns, you might want to consider eating them.

"That's unusual in our culture, but acorns have been a staple in the diet of a lot of civilizations," she said.

There are a number of cookbooks that include ways to use flour made from acorns as well as a multitude of recipes online. The dishes include everything from pancakes to grits (more of a Southern delicacy), from cakes to breads. They also can be roasted like other nuts.

Because acorns contain tannins that critters may love but humans consider bitter, most foragers recommend leaching them before eating them. There are arguments over the best way to do this. Boiling the acorns does it quickly but, some critics argue, removes other nutrients. Soaking the nuts in water for several days also works but, as mentioned, takes several days.

Gupta also warned that getting to the meat inside the acorn is labor-intensive. She and her sons did it once — once, she emphasized — by cracking the nuts open and using a garlic press. "It was a fairly lengthy process."

They eventually made pancakes. "They were dense — filling but nutty," she said. And the process was perfect for kids: "super-messy."

Jeff Strickler • 612-673-7392