Cabbage (Brassica oleracea or variants) is a leafy green biennial, grown as an annual vegetable for its dense-leaved heads. Closely related to other cole crops, such as broccoli, cauliflower and brussels sprouts, it descends from B. oleracea var. oleracea, a wild field cabbage. Cabbage heads generally range from 1 to 8 pounds (0.5 to 4 kg), and can be green, purple and white. Smooth-leafed firm-headed green cabbages are the most common, with smooth-leafed red and crinkle-leafed savoy cabbages of both colors seen more rarely.
It is difficult to trace the exact history of cabbage, but it was most likely domesticated somewhere in Europe before 1000 BC. By the Middle Ages it was a prominent part of European cuisine, although savoys were not developed until the 16th century. Cabbage heads are generally picked during the first year of the plants' life cycles, but those intended for seed are allowed to grow a second year, and must be kept separated from other cole crops to prevent cross pollination. Cabbage is prone to several nutrient deficiencies, as well as multiple pests, bacteria and fungal diseases.
The Food and Agriculture Organization of the United Nations (FAO) reports that world production of cabbage and other brassicas (these plants are combined by the FAO for reporting purposes) for calendar year 2010 was almost 58,000,000 metric tons (57,000,000 long tons; 64,000,000 short tons). Almost half were grown in China. Cabbages are prepared in many different ways for eating, although pickling, in dishes such as sauerkraut, is the most popular. Cabbage is a good source of beta-carotene, vitamin C and fiber. Cabbage when contaminated is sometimes a source of food-borne illness in humans.
A cultivar is a plant or grouping of plants selected for desirable characteristics that can be maintained by propagation. Most cultivars have arisen in cultivation but a few are special selections from the wild. Popular ornamental garden plants like roses, camellias, daffodils, rhododendrons, and azaleas are cultivars produced by careful breeding and selection for flower colour and form. Similarly, the world's agricultural food crops are almost exclusively cultivars that have been selected for characteristics such as improved yield, flavour, and resistance to disease: very few wild plants are now used as food sources. Trees used in forestry are also special selections grown for their enhanced quality and yield of timber.
Cultivars form a major part of Liberty Hyde Bailey's broader grouping, the cultigen, defined as a plant whose origin or selection is primarily due to intentional human activity. Cultivar was coined by Liberty Hyde Bailey and it is generally regarded as a portmanteau of "cultivated" and "variety", but could also be derived from "cultigen" and "variety". A cultivar is not the same as a botanical variety, and there are differences in the rules for the formation and use of the names of botanical varieties and cultivars. In recent times the naming of cultivars has been complicated by the use of statutory Plant Patents and Plant Breeders' Rights names.