At Manhattan's Union Square Greenmarket (Broadway and 17th Street; www.grownyc.org), Keith Stewart is known as the Garlic Guy. Customers rhapsodize about his rocambole garlic—an Italian hardneck variety that may not keep as long as the softneck ones found in supermarkets but more than compensates with its nutty flavor and juicy cloves. At his farm in Western Orange County, New York, Stewart raises more than a hundred varieties of other vegetables and herbs, too, including Asian greens such as mizuna and tatsoi. After 23 years experimenting with new varieties of produce that were once hard to find in New York City, he's gotten very good at what he does, but he gives most of the credit to his customers. "New Yorkers are a savvy, tolerant cross-section of the whole world," he says. "They're always willing to try something new."

The Family Man
Few farmers' markets can match the vitality of the 105-year-old Rochester Public Market (280 North Union Street; www.cityofrochester.gov/publicmarket), which occupies a whopping nine acres in Rochester, New York. Brent Bushart's grandfather, Abe, began selling his potatoes there in the 1930s, and Brent and his son Bryan are following tradition. The Busharts' vegetables draw plenty of customers, but their spuds—creamy Yukon Golds and red-skinned Chieftains, among others—remain their top seller. When the potatoes are newly harvested in late summer, they're tender, at their peak of flavor, and very much in demand.

The Activist
Linger long enough at Ben Burkett's table at the Crescent City Farmers' Market in New Orleans (200 Broadway; www.crescentcityfarmersmarket.org)--piled with okra, collards, and heirloom watermelons he grows on his farm in Petal, Mississippi—and you'll hear his cell phone ring a lot. Maybe it's a local chef like Patois's Aaron Burgau, who plans his menu according to what Burkett has available. Maybe it's someone from the co-op Burkett runs with neighboring farmers. Maybe it's someone seeking assistance from the Federation of Southern Cooperatives, founded to help black farmers hold on to their family farms. In 1995 he also helped found the Crescent City Farmers' Market, and in 2005, after Katrina struck, he helped get it going again. "The hurricane destroyed some—not all—of our crops," Burkett says. "We needed someplace to sell; people needed to eat."

The Innovators
For small-scale poultry producers, having a place to slaughter and process their birds can mean the difference between survival and losing the farm. Back in 1999, Lori and Alan Callister, poultry farmers from West Concord, Minnesota, who sell meat and eggs at the St. Paul Farmers' Market (290 East 5th Street, www.stpaulfarmersmarket.com), decided to take matters into their own hands. "There wasn't a processor near our farm," Lori says, "and we didn't like hauling our chickens long distances." So they set up a processing plant on their property. Today, the Callisters—who raise Cornish-cross and European heritage-breed chickens as well as turkeys, geese, and laying hens—process for more than 50 other nearby farmers, thereby helping to sustain a network of family farms. But for customers, it's really about the Callisters' peerless product: fresh and flavorful in a way that only meat and eggs from happy birds, raised on a small scale and transported a very short distance, can be.

The Artisan
There's no other cheese in the world like Lil Will's Big Cheese. At the Bleu Mont Dairy in Blue Mounds, Wisconsin, cheese maker Willi Lehner washes the rind of this firm, stinky beauty, made with raw cow's milk and aged for 12 months, with a brine containing microbes extracted from the soil on his own farm. It takes confidence to come up with a cheese like that, and in this case it comes of having worked alongside his father, Billi Lehner, a Wisconsin cheese-making legend who learned the craft in his native Switzerland. Today, Willi sells his ten types of cheese at Madison's Dane County Farmers' Market (The Square, 2 East Main Street; www.dcfm.org) and to chefs around the country. Chef Bruce Sherman of Chicago's North Pond, an ardent fan, finds Lehner's approach and his cheeses "deliciously disarming."

The Standard Bearers
In Southern California, where residents have long advanced the "local, seasonal" mantra, the Weiser family—Sid and Raquel and their three grown children—who sell at the Santa Monica Farmers' Market (Arizona Avenue and 2nd Street, www.smgov.net/farmers_market), have a cult following. Vivid orange cauliflower, Red Thumb potatoes, garish and candy-sweet Purple Haze carrots—the kaleidoscope of produce the Weisers grow on their 33-year-old farm in Tahachapi, about 100 miles north of Los Angeles, is considered a gold standard for other small area producers. "Selling directly at farmers' markets allows us to grow for flavor, not shelf life," says Alex Weiser. "Our fruits and vegetables can ripen. They taste better, and they're more nutritious."

The Forager
Foraged foods like mushrooms, wild greens, and berries are in demand all over the country, but the bounty available in the Pacific Northwest's forests is without equal. Jeremy Faber, a tireless forager who sells at the University District Farmers Market in Seattle (_50th Street and University Way NE _www.seattlefarmersmarkets.org), chalks it up in part to the abundance of Douglas fir trees. "Douglas fir probably has the highest number of mycorrhizal mushrooms associated with it of any tree in the world," he says, referring to the symbiosis between fungus and tree root. The Douglas fir's roots can produce mushrooms as varied as chanterelles and lobster mushrooms, much to the delight of Faber's fiercely loyal customers, like chefs John Sundstrom of Lark and Maria Hines of Tilth, in Seattle.

The Convert
In native Hawaiian culture, the taro plant is sacred. Chris Kobayashi, a third-generation farmer who sells the root vegetable at Kauai's Hanalei Farmers' Market (5-5299 Kuhio Highway), therefore takes her job very seriously. Since taking over the family farm in 1990, she has turned to organic practices. In the process, she's become a local celebrity, both for the taro and other vegetables she sells and for the concerns she's raised about the cultivation of genetically modified taro, a threat to native varieties grown and venerated for millennia.