The original wild cabbage is native to the Mediterranean seaboard, and this salty, sunny habitat accounts for the thick, succulent, waxy leaves and stalks that help make these plants so hardy. It was domesticated around 2,500 years ago, and thanks to its tolerance of cold climates, it became an important staple vegetable in Eastern Europe. The practice of pickling it appears to have originated in China.
Collards, kale, and Portuguese tronchuda cabbage resemble wild cabbage in bearing separate leaves along a fairly short main stalk; tronchuda has especially massive midribs. Cultivated cabbage forms a large head of closely nested leaves around the tip of the main stalk. There are many varieties, some dark green, some nearly white, some red with anthocyanin pigments, some deeply ridged, and some smooth. In general, open-leaved plants accumulate more vitamins C and A and antioxidant carotenoids than heading varieties whose inner leaves never see the light of day. Heading cabbages often contain more sugar, and store well for months after harvest.