"It kind of looks like a Mudhole," I say, referring to a type once known in these parts for making excellent apple butter. I take a bite. Nope, this one is creamier, with whiter flesh. It's probably just one of the countless unnamed apple varieties you find in the wild around here.

"That's the dilemma," Jim says, as we get back in the car. "There are so many heirloom varieties that have adapted to the micro climates up here, it's hard to identify them." Jim, a lanky, bearded 35-year-old, knows a lot about heirloom fruits and vegetables. He works with the Southern Seed Legacy in Athens, Georgia, an organization devoted to preserving the seeds of heirloom plants in order to restore some of the genetic diversity that industrial agriculture has eroded over the years.

On this trip, though, we're looking for forgotten fruits, not seeds. We're on a late-summer apple search-and-rescue mission in the mountains of North Carolina for a program I started five years ago called Renewing America's Food Traditions (RAFT). With the help of Slow Food USA and six other national organizations, RAFT aims to restore foods and culinary customs that are at risk of disappearing. Apples are at the top of our list because hundreds of varieties have become extinct in recent decades, their unique physical attributes and tastes basically erased. For a food that is as iconic and as essential to the American culinary canon as the apple, it's tragic that only 11 varieties—out of the estimated 14,000 that evolved from the seeds English settlers brought to North America from Europe—constitute 90 percent of all apple consumption in the United States.

The remaining 10 percent includes heirloom apples of all shapes and sizes—some gnarly and spotted and downright ugly, others with graceful silhouettes and glossy skin. Some are honey sweet; others have a lip-puckering, tannic tartness; still others fall somewhere in between, offering subtle hints of flavors most people may never have tasted in an apple. They have names like Gloria Mundi, Seek-No-Further, Ohio Nonpareil, Brushy Mountains Limbertwig, and Shiawassee Beauty, to name just a few. The problem is that fewer and fewer of these fruits are commercially available, as one small orchard after another is let go to seed and the names of the old varieties are forgotten. The trees themselves may survive, in the wild or on private property, but the histories of their fruit are often a mystery.

That's one reason why I'm driving the country roads of North Carolina with Jim: I'm meeting up with locals who can help me identify and revive some of these old varieties. This part of Appalachia—particularly the region known as the Southern Highlands, which encompasses the Blue Ridge, Great Smoky, and parts of the Cumberland and Allegheny mountain ranges—is one of the richest apple habitats in the country. Today, somewhere between 800 and 1,000 distinct heirloom varieties still grow in the area's hills, coves, and hollers—more kinds, by some counts, than are found in all the other regions of North America combined.

Not surprisingly, the cooks of Appalachia have strong preferences for specific varieties—one kind for eating fresh, another kind for applesauce, another for pie, and so on—that are different from the tastes of their Northern neighbors. "In the North, they eat a tart and cook a sweet. Here in the South, it runs the other way," one North Carolina orchard owner tells us. "I love a tart Jonathan in a pie, but those Yankees might use an apple as sweet as a Golden Delicious." What's more, Appalachian cooks use apples in some altogether remarkable ways. Outside Appalachia, you just aren't going to find so many people inclined to make fried apple pies, cook sliced apples with chopped cabbage, spread applesauce between layers of molasses cake, stew sun-dried apples, or dip ringlike slices of apples in batter and fry them to make fritters.

To people like me, the disappearance of old apple varieties—like the die-off of an animal species—represents a profound loss, in terms not just of botanical diversity or rural cultural history but also of the way we eat. The striking, unusual flavors and cooking properties possessed by these heirloom apples simply don't exist in supermarket varieties. And yet, Jim reminds me, most people in the region don't refer to the apples growing in their midst as heritage breeds. "Most people around here have never heard the term heirloom applied to plants," Jim says. "They just call them old-timey apples."

In the broadest sense, an heirloom apple is any distinct, named variety of the fruit that has been passed down in a family, community, or culture for generations. To preserve an heirloom variety, it's not enough simply to save the seeds, though. Growing a genetically identical apple requires a concerted, calculated effort: you have to graft cuttings from one tree onto the rootstock of another. The reason for this is that seedling apple trees—those that grow in the wild from seed—produce fruit that's essentially a hybrid of their parents and therefore a new kind of apple. This explains why countless varieties of the fruit, believed to have originated in Kazakhstan thousands of years ago, have propagated around the world.

My trip in North Carolina with Jim is just the latest in a series of travels I've made with RAFT collaborators over the past few years to seek out, recruit, and learn from other Southern heirloom apple preservationists. These journeys have led me to forge friendships with some remarkable people—orchard keepers, historians, cider makers, horticulturists, and others. Perhaps the most respected scholar among them is the North Carolina apple historian Creighton Lee Calhoun Jr., who spends the majority of his waking hours matching forgotten fruits to their names. Since he took up this pursuit, in 1982, he has discovered and identified a slew of apples formerly thought to be extinct, relying mostly on horticulture books, old nursery catalogues, and archival illustrations. Calhoun, a soft-spoken 75-year-old, has also brought 300 heirloom varieties into cultivation at nurseries he consults with across the South.

In 1995 Calhoun published Old Southern Apples (McDonald & Woodward Publishing Company), a lavishly illustrated tome that has become a bible for apple preservationists. Not only does the volume present detailed descriptions of some 1,600 varieties, but it also brings to life the people and histories wrapped up with this food. He describes the significance of the apple in the rural South, where, before the days of refrigeration, it was the only fruit that could be kept through the cold months "to provide a taste of freshness." Of the elderly Southerners who helped him reclaim knowledge about heirloom apples, Calhoun writes, "They remember storing boxes of apples through the winter in unheated rooms...how those apples perfumed the whole house. They recall drying apple slices on a tin roof, and they can tell you how to make cider and vinegar. But most of all, they remember the incomparable taste of a freshly picked southern apple...baked right on the tree by those long, hot southern summers."

Other apple preservationists I've met are more recent converts to the cause. One of them, Tom Brown, is a retired chemical engineer in his late 60s who lives in Clemmons, North Carolina. In 1998 he became obsessed with a juicy variety believed to be extinct called Harper's Seedling and has since tracked down at least seven locales near his home where those apples once grew; he took cuttings from a surviving tree in the area just before it died and grafted them onto trees on his property in hopes that, in a few years, he will have a steady supply of the delicious fruits. His hunt for Harper's Seedling has fueled a passion for finding other forgotten varieties. These days, Brown estimates, he racks up at least 20,000 miles a year on Southern back roads, traveling as far as Kentucky, Virginia, and Tennessee to chase down leads given to him by old-timers at regional festivals, people who grew up with these apples and can remember their names and characteristics.

"Time is running out," Brown told me when I ran into him at the Forgotten Fruits Summit, the first annual powwow for apple preservationists, held in Madison, Wisconsin, last March. "I recently picked up a picture I had taken of the six folks who had helped me the most in my search for apples, and I realized that five of them had died."

At that same summit, I met up with another dedicated preservationist: an orchard owner from Boone, North Carolina, named Bill Moretz. His orchard was started by his grandfather in the 1930s and is now home to one of the country's first community supported agriculture projects devoted to promoting apple diversity. Once a week, his customers receive a bag of several different kinds of heirloom apples.

One of their favorites is the Sweet Dixon, a dessert apple that has red-striped skin and crisp, sugary-sweet flesh. The story behind the Sweet Dixon, which was widely thought to have disappeared, goes like this: Seventeen years ago Calhoun got wind that an elderly North Carolina woman had a huge old Sweet Dixon tree on her property that still produced fruit. By the time he arrived at her home to take cuttings, however, the tree had been cut down. Sensing Calhoun's disappointment, the woman managed to find another tree growing nearby, one she remembered from her childhood; he took cuttings and has been growing Sweet Dixons ever since. What Calhoun didn't know until years later—when he was asked by Moretz to identify an old tree growing near his barn—was that the same kind of apple had been growing on Moretz's property all along.

Toward the end of our North Carolina trip, Jim Veteto and I decide to visit Moretz at his orchard. When we arrive, he hands us a couple of Sweet Dixons straight from the tree to sample. Then he picks one for himself and takes a bite. "It's still green yet," Moretz says, "but you can taste all the sugars and the flavors developing." It is clearly one of his favorites, but Moretz, like many other orchard keepers dedicated to bringing back as many old varieties as they can, is reluctant to proclaim the flavor of any single apple to be better than that of others.

Moretz's orchard, which is home to 100 different varieties of apple, is a supremely serene place, a grid of tidily pruned trees in evenly spaced rows that extend over rolling hills. The air is fragrant with fruit, and the grass underfoot is lush. Resisting the temptation to lie down right where I stand and soak up the scene, I follow Moretz as he makes his rounds, stopping before every other tree to examine its apples and the health of its bark, branches, and leaves.

Watching Moretz tend to his orchard of rare fruits, I come to the realization that it's more than nostalgia that drives people like him to keep such historic apple varieties alive. It's the sheer love of the food itself, in all its incarnations, and the joy of sharing them with friends and passing them on to a new generation. "I grow them to embrace the future," he says to Jim and me before we leave. "But it's not enough just to grow them. You have to eat them, too."