The local growing season here runs roughly from mid-May to early October. A restaurant committed to local sourcing must therefore answer a question that coastal restaurants can avoid: what does local mean in February?

The honest answers are stored, preserved, greenhouse-grown, or nothing.

Minnesota chefs who took the commitment seriously spent the last fifteen years rebuilding preservation techniques that had largely left professional kitchens. Fermentation, canning, curing, root cellaring, drying — practices that were standard in this climate a century ago and were then made unnecessary by national distribution.

The results have been better than nostalgia would predict. Lacto-fermented vegetables, properly done, are not a substitute for fresh produce but a different ingredient with its own range.

"We stopped apologizing for winter," a chef whose restaurant in Northeast has run a local-sourcing program for a decade said. "February is a season. It has a flavor. It tastes like fermented cabbage and wild rice and animals that ate grass in August."

The economics are less romantic. Preservation requires labor in the fall, storage space through the winter, and capital tied up in inventory. A restaurant that puts up four hundred pounds of tomatoes in September pays for them in September and sells them in March.

Small farms, correspondingly, have built businesses around a compressed selling window and have increasingly moved toward season extension: high tunnels, hoop houses and cold-hardy crops that push the harvest into November and restart it in April.

Greenhouse production has expanded, particularly for greens, though the energy cost of growing lettuce in a Minnesota January is a legitimate question that the locavore accounting does not always address honestly.

Wild rice occupies a category of its own. Hand-harvested from lakes by Ojibwe and Dakota harvesters under treaty-protected rights, it is genuinely local in a way no cultivated crop matches, and the distinction between it and the paddy-grown cultivated grain sold under the same name is one that chefs have worked to make legible to diners.

The most successful local-sourcing restaurants have concluded that the commitment works only if it is specific. A menu that says local means little. A menu that names the farm, and changes when that farm's crop ends, means something.