It takes a tough nut to thwart a former wrestler and offensive lineman.

So imagine what happened when Mike Fredenburg, who was on the Bulldogs offensive line in the early '90s, discovered a black walnut tree in his yard in Ball Ground.

LOUIE FAVORITE/Staff (ENLARGE)

Mike Fredenburg and his 6-year-old son, Joseph Scherer, shell black walnuts in their Ball Ground garage.

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Tough guy met legendary tough nut. Bones weren't broken, but pliers were bent.

But we're getting ahead of the story. For his first foray, the former University of Georgia player did what countless other black walnut lovers have done: Threw the nuts on the driveway, got out the truck and started running over them. The hulls gradually slipped off.

He still had to get through the thick shells. A broken pair of pliers and an $80 vise later, Fredenburg, his wife, Jennifer, and their son, 6-year-old Joseph Scherer, are slowly extracting the nut meat and selling it for $10 a cup on craigslist.com.

"It should be $100 a cup, as much work as it involves," Fredenburg says. "But it's fun."

Black walnuts, beloved by an often rural fan base for their emphatic, slightly bitter flavor, make their way into stores in much the same way. An informal network harvests nuts from wild trees in the fall and takes them to more than 250 hulling stations scattered across the main growing region of 15 states in the Appalachians and the Midwest.

From there, the nuts go through one Missouri processing company that removes the shells by running them between large steel wheels, pulls out the precious 7 percent of usable nut meat and gets it into the hands of commercial ice cream makers, eager home bakers and those willing to pay more per pound than what strip steak fetches.

The appeal lies in the nut's intense, earthy flavor and its link to a number of heritage recipes. A few black walnuts go a long way, adding a savory, slightly bitter flavor to the sweets in which they're typically used. The trees are native to America, unlike the English walnut.

The Hammons Product Co., based in the heart of black walnut country in Stockton, Mo., has outlasted most of its competitors to supply almost all of the nuts. Some go to commercial customers such as Mayfield Dairy Farms and Blue Bell Creameries. About 45 percent of Hammons' nuts wind up in black walnut ice cream. The rest ultimately go to home bakers or are sold to small candy companies.

It's a somewhat precarious trade, depending on an inconsistent supply of nuts and on a core group of aging black walnut lovers who seek out the flavor in ice cream, fudge and other goodies.

Mayfield, for example, selects new ice cream flavors by letting customers sample possibilities and vote for their favorites. Black walnut wouldn't make it through that popularity contest, company President Scottie Mayfield once said, but it commands a faithful niche market and stays in the lineup.

Poor sales led spice giant McCormick & Co. to drop its black walnut extract in 2005. Kroger stopped stocking the nuts that same year, although it is looking for a supplier for the holiday baking season, spokesman Glynn Jenkins says.

Unlike mild English walnuts, black walnuts aren't commonly eaten out of hand. They're an ingredient best used to complement other flavors.

Hammons wants to make the walnut supply more secure. More than 99 percent of its nuts come from wild trees, says Brian Hammons, who is president of the company his grandfather started more than 60 years ago. The tree's wood, prized for making durable gunstocks, is far more valuable than the nuts.

The company is funding research into thinner-shelled black walnuts that will be easier to process and yield more nut meat, making them more appealing to farmers and assuring a more constant supply. This year the company processed just 12 million pounds, down from about 30 million last year, due to a combination of weather and an off-year for nut harvests. (Many nut trees produce larger harvests in alternate years.)

Hammons also wants a more secure market. The company is studying college students, trying to find black walnut dishes that appeal to them. Among the attempts: caramelized black walnut ice cream with candy coating around the nuts, clam linguine with black walnuts and a salad.

"It's an acquired flavor," Hammons says. "It has always been a little bit of an older consumer, and part of that is just the maturing of the palate."

Still, those palates keep maturing. The company wants to make sure there's another generation of customers.

"We realize one of these days that some of the older consumers who are the base will be gone," Hammons says.

Fredenburg had never tasted the nuts before moving to Ball Ground this year and tracking down the identity of the golf ball-size green orbs that rained down on the yard by the thousands. When he and Jennifer tried a few, they worried about the bitterness.

"My wife thought, 'Oh, they're no good.' We took some of them to a friend who's in the horticultural business, and he said, 'Oh, no, that's perfect. It's exactly what they're supposed to taste like.' "

Once added to black walnut cake and ambrosia, though, the nuts were marvelous, Fredenburg says.

Although this year's harvest is small, there should be enough nuts for holiday bakers making cakes, brittle and quick breads. Savvy cooks pay $12 to $14 a pound for shelled nuts, found in many grocery stores this time of year, and stick a couple of big bags in the freezer for summer ice cream.

Otherwise, they're left with finding a friend with a tree, revving up the Ram and pulling out a hammer.

The shell is much thicker than that of an English walnut, and no ordinary nutcracker will work. The hull is even harder to penetrate. Running over it in the driveway works, but only if you're on gravel. The hulls, prized by weavers for the deep brown dye they produce, will stain concrete and hands.

Corinna Garmon, who boxes farm products weekly for members of the Spruill Green Market community-supported agriculture program, recently included some black walnuts.

With a farm to run and the market to manage, she left the time-consuming shelling to subscribers. The nuts were already hulled, after spending a few weeks in the driveway of her godmother's North Carolina home.

When Garmon wants to use some, usually to make banana bread, she turns to the solution that many black walnut lovers have hit upon.

"I send my son outside with the hammer and say, 'Here,' she says. "He's 12, and he loves doing that."

It's a tough nut. But it's easy to love.