The thickest crop of black walnuts in memory has been falling on campers, car hoods and heads in recent weeks, exciting tree growers, some bakers and millions of squirrels from the metro area to the Iowa line.

"They're big and fat and dropping all over the place," said Joe Deden, director of the Eagle Bluff Environmental Learning Center near Lanesboro, Minn.

Dave Palmquist, naturalist at Whitewater State Park, said it's the best crop he's seen in his 38 autumns at the park.

"In some campsites, it's like walking on ball bearings," said Palmquist, who marked his 60th birthday last month with a customary black walnut cake, made with last year's slimmer pickings. "Driving down the road, you hear 'Pop-pop-pop!' I was out mulching underneath this one walnut [tree] and I literally was concerned for my safety."

Walnuts, like acorns, vary in abundance from year to year. This year's cool, wet spring would ordinarily have reduced the pollen needed for the walnut crop, Palmquist said. But simple good timing may have overcome that.

"The last couple of years have not been very good, so maybe it was just time for them to invest in reproduction. I think we're going to have real good squirrel survival this winter, too."

The Minnesota Department of Natural Resources and at least one private tree nursery buy black walnuts from anyone willing to collect them. This year, paying about $5 per bushel, the DNR easily filled its quota of about 1,000 bushels; Jon Alness, owner of Zumbro Valley Forestry near Rochester, maxed out at 3,000. A bushel of still-in-the-hull walnuts, which resemble large limes, weighs 44 pounds.

The stuff new trees are made of

Both the DNR and the private nursery use the nuts as seeds for new trees. Most plantings are intended to replace logged-off hardwoods, or to start woods on land protected from farming or development.

Southeastern Minnesota is at the northern edge of the natural range of black walnut. But because the tree grows more slowly in Minnesota than farther south -- maturing in 35 to 50 years -- its grain is tighter and more highly prized for furniture and other fine woodwork. The hard shells of the nuts themselves are often used in abrasives, even in facial scrubs, and for traction on boat decks. In the short term, the nuts nourish wildlife and find their way into kitchens -- but only after considerable hand (or foot) labor.

A tough nut to crack

Anyone can gather walnuts from state parks, Palmquist said. If you're not a squirrel, you would run them through a corn sheller or a drum lined with rubber spikes to remove the hull. Other methods: stomping on them or lining them up in the driveway and driving over them. The removed hulls are often used in dye-making and are famous for staining the fingers and clothes gold to dark brown. After the hull is removed, the roughly 1-inch-diameter nuts need to be spread out to cure in a cool and dry place for about two weeks, then stored in a cool well-ventilated place.

Anyone planning to eat the nuts learns they are quite different from the thin-shelled "English" walnuts sold in grocery stores. Getting at the black walnut meat requires some time with a hammer or vise to crack open the tightly sealed, wood-like shells, then some fine-grained destruction with pliers and wire cutters. The nut meats most often are extracted in small, broken bits.

Annamarie Rigelman, pastry chef at Lucia's restaurant in Minneapolis, said the nuts are unlikely to turn up anywhere on the menu there. They've not been available in recent years, she said, and when they have been, they've been expensive. Plus, they have what she called "an assertive flavor."

"They're an acquired taste. That's the best way to describe it," she said. "We've had them in the past 10 years, but they didn't go so well."

Bill McAuliffe • 612-673-7646