In some restaurant kitchens, they mean a larder full of root vegetables, grains, dried beans and cellared fruits, as well as a lot of curing, pickling and preserving. Other, more ambitious restaurants turn to greenhouses or new vegetable hybrids.
And many inevitably resort to a certain amount of well-intentioned cheating.
"At some point, you're inherently a hypocrite," said Marc Meyer, the chef at Cookshop, in Chelsea. "You can't make a menu of turnips, rutabagas and potatoes."
Even chefs like him who are devoted to local and seasonal foods have to make exceptions, including the occasional FedEx package. Mr. Meyer's winter menus include dishes that straddle the indigenous and the imported, like line-caught Long Island swordfish with cauliflower (also from Long Island) and chicory (from Florida), dressed with Meyer lemon (California) and topped with wedges of blood orange (California again).
Total purity, Mr. Meyer said, is a nice idea, yet all but impossible: "What about chocolate? What about olive oil? Spices?"
"Go for it if you can," he added. "I just can't with a 100-seat restaurant."
At Rouge Tomate, an Upper East Side shrine to fresh local produce, the executive chef, Jeremy Bearman, admits to using the occasional nonlocal winter ingredient, particularly tropical fruits (bananas, mangoes, pineapples) in desserts. "I don't think you can be one of those restaurants here in the Northeast saying, only things from 50 miles away," he said.
Certainly, there are outliers who go to extreme lengths to keep the faith. At Willows Inn, on Lummi Island in Washington State, Blaine Wetzel uses only ingredients grown on the restaurant's farm and surrounding farms.
"We are as purist as it gets," Mr. Wetzel said. This means that "if I want lemon juice in something, I have to find an alternative" - underripe gooseberries are a common solution - "or maybe it's not the right dish to be on the menu." He forages for wild winter mushrooms and stores hundreds of onions bought from a neighboring farm. Yet despite the relatively moderate winter microclimate, in a shallow bay protected from cold ocean winds by the Olympic Mountains, Mr. Wetzel shuts down his restaurant in December and January. "We close when we can't do what we do," he said.
Dan Barber's kitchen at Blue Hill at Stone Barns, in Pocantico Hills, N.Y., buys many of its ingredients from the Stone Barns Center for Food and Agriculture, an independent nonprofit organization on the same grounds that operates 80 acres of farmland (6 1/2 of them for vegetables), a 22,000-square-foot greenhouse and outdoor rows of plants shielded by a protective covering.
In addition, he and his team (as well as a full-time vegetable farm manager, Jack Algiere, and his crew) work with agricultural scientists at Cornell University on breeding winter-friendly vegetables, including a small, intensely sweet butternut squash they call the honeynut.
Mr. Barber pointed out that many of the strategies that chefs employ in winter, like fermentation or cold storage, are nothing new. "A lot of these techniques are ancient and brilliant, and evolved out of desperation," he said.
Perhaps buoyed by the more modern technologies involved in breeding, he said that in some ways he preferred cooking in the winter months. "At what point can I make the greatest impression?" he said. "People's expectations are lower, and it's easier to exceed them."
Mr. Barber isn't the only chef who welcomes the cold-weather challenge. "We sort of look at winter the way an old-school chef looks at frugality," said Jonathon Sawyer of theGreenhouse Tavern, in Cleveland. "We take more time with dishes because we have less to put on the plate."
Mr. Sawyer, whose restaurant's Web site includes a manifesto on "Sustainability Initiatives," bottles his own line of vinegars, including ones made from craft beer and rosé wine, and has a running stock of preserved items. He said relationships with local farmers become all the more important in winter, for securing ingredients like grains (in particular, farro, an Ohio specialty), shelled beans and legumes.
But even the word "local" can fall prey to some fudging.
"There's a very famous farmer who, when I met him years ago, had a 20-mile radius" of restaurants he'd sell to, Mr. Barber said. "And last year when I talked to him, he said he was delivering to a restaurant 28 miles away."
What happened to 20?
"All purists have their negotiables," Mr. Barber said.
Iliana Regan, whose Chicago restaurant, Elizabeth, has won attention for its emphasis on local ingredients, many of them foraged by Ms. Regan, has a somewhat broader definition. Almost everything on her menu "is Midwestern, though perhaps out of state lines," she said. "We're probably breaking the 200-mile rule."
Whence 200? "I believe I read it somewhere," Ms. Regan said.
Thanks in part to her restaurant's small scale (there are three set seatings for eight people each), Ms. Regan can quickly adapt whatever ingredients come her way. Raccoon from a Wisconsin hunter became a pâté, which she paired with pickled cranberries. Mushrooms foraged on her cousin's Indiana farm were partly frozen, and thus unsuitable for serving conventionally, so she dehydrated them and made a tea.
But Ms. Regan has her limits: she supplements her menu with items from Whole Foods - "everything from squash to parsnips to dairy," she said, adding, "at least that way I can see if it's organic and where it's from." And like many chefs, she imports specialty items from around the world, like matsutake mushrooms from Japan and truffles from Europe.
If there's one thing about winter cooking that chefs seem to agree on, it's that the toughest time isn't the middle of the season, but the end. "For me, the hardest months are March and April," Mr. Barber said. "Storage starts to run out and you're sick of the root vegetables."
The result, for some, is chef-envy. "I went down to San Francisco a couple of weeks ago," Mr. Wetzel said. "It was making me jealous. Things I don't see until June or May, they have on their plates in December."
For Mr. Bearman of Rouge Tomate, flying in an item or two is particularly tempting in late winter, when customers expect early-spring all-stars like ramps and asparagus. "There's definitely times where, if we see great fava beans or great peas coming out ofIacopi Farm in California, we probably cheat a little bit," he said. "But then we switch when it comes into season here."
By some measures, circumstances for Northern chefs are improving. Mr. Meyer noted the increased vibrancy of farmers' markets, including the Greenmarket initiative in New York. "A few years ago, there was no radicchio, no treviso," he said. "You're seeing more variety."
Others even see a benefit from global warming. "I hate to say it, but it's true," Mr. Sawyer said. "We got artichokes in Ohio all the way into November this year. Maybe December."
Then again, restraints are sometimes a good thing. Mr. Bearman said the bounty of late summer could be overwhelming: "You find yourself thinking, 'What am I going to do on my menu?' "
Reprinted from The New York Times