SALAD DAYS.

Doucette, they called it, the sweet little one, and its lack of cultivation was half its charm. It was a slender, diminutive thing--so lowborn that it came clean only after repeated washings--but it had strong roots and surprising snap, and a certain native, untutored delicacy. Alexandre Dumas found it "very tender and very tasty," and Thomas Jefferson always kept a place for it at Monticello. Balzac wrote parts for it in his novels, and the great food writer Waverly Root warned against dressing it too finely, lest its "modest, subtle, seductive, and caressing" character be compromised. Even its admirers admitted that it was still a bit wild: an unimproved little weed that no one had ever bothered to take in hand. But they liked it well enough as it was.

"It's beautiful," Todd Koons told me one evening. "But it's a little leggy." We were sitting in a restaurant on a lamp-lit side street in Carmel, California. Koons, who is forty-four, was wearing a cream linen shirt with the sleeves rolled up, and, like a lot of people in Carmel, he looked as if he'd just had a long, relaxing mud bath. He had burnished skin and sun-bleached hair, loose shoulders, and an easy, half-mocking smile. Peering intently at his salad bowl, he reached in with his thumb and forefinger and lifted out a sprig of doucette, or mache, as it's now commonly known in the United States. Its eight spoon-shaped leaves were clustered in a perfect rosette, but Koons wasn't impressed. "It's too big and it's overdressed," he said. "Ideally, there would be just six leaves, and the whole thing would fit in your mouth." He shook his head and sighed, then ate the mache anyway. "One of my most valuable lessons has been that I am not my salad," he said. "I am not my mache. Just because my mache is having a bad day doesn't mean I have to have a bad day."

Koons is a farmer, an entrepreneur, and the president of a produce company called Epic Roots. He has been called the Johnny Appleseed of salad, but he's more like its Colonel Tom Parker: he takes obscure country greens and grooms them for mass consumption. He first came across mache as a young boy in Oregon, living on a small hippie farm near Eugene. His parents were artists and epicures--a rare combination in the nineteen-seventies--who worked with stained glass and raised their own rabbits and vegetables. Dinners were long, talky affairs lit by kerosene lamps, often with other artists and intellectuals around the table, and Todd was in charge of the salads. At first, he didn't really notice the mache--its taste was too subtle to stand out among the other greens. But one visitor almost certainly did. Alice Waters, the owner of Chez Panisse, in Berkeley, came to dinner in 1975 as the guest of a local art patron and gourmet. Afterward, when she heard who had made the salad, she teasingly invited Koons to come see her when he finished high school. Three years later, at the age of eighteen, he showed up and asked for a job.

Chez Panisse was, of course, the wellspring of a new kind of American cooking in those years. Waters, who opened the restaurant in 1971, when she was twenty-seven years old, reminded a generation of chefs of the virtues of fresh, local, seasonal produce, and salad was her prime proselytizing tool. In the late seventies, when three-quarters of the lettuce sold in this country was still iceberg, Waters was serving organic mesclun--a spicy bramble of leaves from a dozen or more kinds of plants, flanked by rounds of baked goat cheese, which was considered equally exotic. "That was the salad that changed America," the restaurant consultant Clark Wolf told me recently. "It taught us that greens aren't necessarily bland and wilting, that they can be peppery and sweet and nutty and creamy. It taught us that they can make a different dish in every season, as the crops and flavors change. And, once we knew that, it changed the way we felt about everything. If salad wasn't just iceberg with a slice of radish on top, then what about other vegetables? What about chickens and cheese and milk and grains?"

In the years since Chez Panisse opened, American produce has been virtually reinvented. Organic vegetables can be bought at Piggly Wiggly, and last year McDonald's sold a hundred and fifty million "spring mix" salads--their drastically simplified version of mesclun. Bagged salads, featuring plants that people once attacked with hoes and herbicides, are a two-and-a-half-billion-dollar industry. Koons and Waters have been central figures in this revolution. For a few years after he arrived at Chez Panisse, they also dated. But in recent years they've taken organic farming down radically diverging paths. While Waters has continued to preach "slow food" and small farms, Koons has focussed on broadening the repertoire of industrial agriculture. Mache is his latest protege. If he was slow to appreciate it at first, he has come to think of it as the perfect salad green: sophisticated enough for gourmets yet amiable enough for a truck-stop diner. The French grow fifty million pounds of it a year, and Koons believes that Americans could consume four times as much. "It's going to be big," he says. "It's going to be a mother."

First, though, it must be made to cooperate. Like a lot of salad greens, mache is more than a little passiveaggressive. It will agree to grow most anywhere, just not particularly well. It's native to the Alps, so to withstand the California sun it must be kept in shade at all times, like some pale Victorian beauty. When picked fresh in the wild, it's subtle and complex, with a faint taste of hazelnuts and newly mowed grass. In a farmer's hands, it can turn flabby and insipid. How do you shape so delicate a thing for the blunt tastes of the American consumer? How do you turn it into a uniform and predictable product, one that lends itself to mechanized harvesting and washing, can last for weeks without wilting, and yields enough to justify all the money that's been poured into it? How do you make a widget out of a weed?

"A lot of this isn't about ...