The growing season never seems long enough. But one group of vegetables can help you extend it at both ends: the hardy and versatile brassicas. A single species, Brassica oleracea, has given rise to cabbage, Brussels sprouts, broccoli, Chinese broccoli, kohlrabi, kale, collards, and cauliflower. A related species, B. rapa, includes (confusingly) the plants we know as Napa cabbage and broccoli raab, mizuna, bok choy, turnips, and the mustard crop whose seeds are the source of canola oil.
These members of the mustard family (Brassicaceae) are also known as cruciferous vegetables or cole crops, a name derived from the Latin caulis, meaning stem. That hints at their long history of cultivation in central Asia and the eastern Mediterranean; the classical Greeks and Romans grew at least three separate cole crops descended from the wild cliff-dwelling cabbage plant.
Over the centuries, selective breeding of wild brassica species to emphasize leaves, flowers, or roots has led to the wide variety of these sturdy, nutritious vegetables. There’s been a boom in brassicas, especially broccoli, in the past couple of decades, after researchers reported possible links between diets high in cruciferous vegetables and lower risks of some kinds of cancer. This possible health connection may be due to sulfur-containing compounds called glucosinolates. (The sulfurous compounds are also responsible for the unpopular aroma of overcooked cabbage or Brussels sprouts.) More recent research has tempered some of the earlier enthusiasm, however, and scientists now say that further work is needed to demonstrate whether or not brassicas play a role in preventing cancer. But there remains no doubt that cruciferous vegetables, especially broccoli, are rich sources of vitamin C, folate, carotenoids, and other beneficial compounds, as well as abundant fiber, known to deter colon cancer.
The bad news is that the benefits are greatest if cole crops are eaten raw. Cooking breaks down the beneficial compounds and dissipates the vitamins. Slaw, anyone? Or broccoli sprouts? If you can’t choke down raw broccoli, the best alternative is to cook these vegetables as little and as lightly as possible—a quick steam, stir-fry, or sauté rather than a slow stew.