Whereas just a decade or two ago supermarket produce aisles offered a virtually unchanging cast of bare basics, today's food stores and farm stands are bursting with unprecedented variety. Even familiar salad vegetables now appear in numerous incarnations—heirloom tomatoes of every size and color, purple carrots, cucumbers both great and small. We have red onions, white onions, yellow onions, vidalia onions, walla walla sweet onions, not to mention spring onions, scallions, shallots, and a whole range of chives. Garlic, once considered too aggressive for a gentleperson's table, is now ubiquitous in our salads. The selection of greens one can buy today is also staggering: formerly obscure finds, including such chicories as radicchio, chioggia, and the long, serrated puntarelle of winter, are no longer uncommon. Many kinds of cress and fresh herbs can now easily be bought year-round. And almost any market sells bags of washed mixed greens under the name mesclun. Contributing to this diverse tableau are once exotic vegetables like bean sprouts and mizuna and tatsoi (a cousin to bok choy) greens.