Beet belongs to the genus Beta in the goosefoot family, Chenopodiaceae. There are several varieties of beet and all are used as food for either animals or humans. Most species of beet are biennial and are harvested after the first growing season when the roots are most nutritious.
The wild beet, Beta maritima, is thought to be the species from which cultivated beets (Beta vulgaris), originate. Wild beet is found on the Mediterranean and Atlantic European coasts. Although beets are native to these temperate areas, they are now cultivated in many parts of the world for food, fodder, and as a source of sugar.
The cultivated beet has several commonly used varieties. Probably the most recognizable agricultural beet (Beta vulgaris escuelenta) is the bulbous, reddish-purple root that shows up on the dinner table. Although these beets can be successfully stored during winter, most of the crops of red garden beets and table beets in the United States are canned, pickled or frozen. The red beetroot is often dried, made into a powder and used for food coloring and fabric dyes. Beet plants can have round globular, or long conical roots with several stems growing above ground. The leaves on the stems vary in size and from green to purple in color.
Another important variety of the cultivated beet is B. vulgaris crassa, the sugar beet. Sugar beets are quite large, with green leaves and white roots weighing about 2.2 lb (1 kg). The root is shredded, mixed into water, and heated. The impurities are removed and the remaining sugary liquid is concentrated and crystallized. The sugar beet has been cultivated for centuries, but its use as a primary source of sugar dates back to the beginning of the nineteenth century. France is a leading contributor to the world's sugar beet stores, which today maintains half of the world's sugar supply.
Although beets are usually grown for the root part of the plant, one type of common beet is grown for its greens. This beet is known as Swiss chard (variety B. cicla), or spinach beet, and has large stems, fleshy red and green curly leaves, and small, branched roots. The Mangel-Wurzel beet (variety B. macrorhiza) has large roots and is grown for livestock feed. Most of the nutrients in beets are found in the tops, which are used as greens. Swiss chard, for example, is a good source of vitamins A, B1, and B2, as well as calcium and iron.