The beet (Beta vulgaris) is a plant in the beet root family. It is best known its numerous cultivated varieties, the most well known of which is probably the red root vegetable known as the garden beet. However, other cultivated varieties include the leaf vegetables chard and spinach beet, as well as the root vegetables sugar beet, which is important in the production of table sugar, and mangelwurzel, which is a fodder crop. Three subspecies are typically recognised. All cultivated varieties fall into the subspecies Beta vulgaris subsp. vulgaris, while Beta vulgaris subsp. maritima, commoly known as the sea beet, is the wild ancestor of these and is found throughout the Mediterranean, the Atlantic coast of Europe, the Near East, and India. A second wild subspecies, Beta vulgaris subsp. adanensis, occurs from Greece to Syria.

The beet has a long history of cultivation stretching back to the second millennium BC. The plant was probably domesticated somewhere along the Mediterranean, whence it was later spread to Babylonia by the 8th century BC and as far east as China by 850 AD. Available evidence, such as that provided by Aristotle and Theophrastus suggests that the leafy varieties of the beet were grown primarily for most of its history, though these lost much of their popularity much later following the introduction of spinach. The beet became highly commercially important in 19th century Europe following the development of the sugar beet in Germany and the discovery that sucrose could be extracted from them, providing an alternative to tropical sugar cane. It remains a widely cultivated commercial crop for producing table sugar.

Beta vulgaris is a herbaceous biennial or rarely perennial plant with leafy stems growing to 1-2 m tall. The leaves are heart-shaped, 5-20 cm long on wild plants (often much larger in cultivated plants). The flowers are produced in dense spikes, each flower very small, 3-5 mm diameter, green or tinged reddish, with five petals; they are wind-pollinated. The fruit is a cluster of hard nutlets.

Taxonomy

The taxonomy of the various wild and cultivated races of beets has a long and complicated history. Mansfeld's Encyclopedia of Agricultural and Horticultural Crops following Letschert's 1993 treatment of Beta section Beta recognizes the following taxa:

• ''Beta all cultivated varieties of the beet, which are grown for their tubers, leaves, or swollen midribs.
• B. v. ssp. vulgaris convar. cicla (leaf beets) - The leaf beet group has a long history dating to the second millennium BC. The first cultivated forms were believed to have been domesticated in the Mediterranean, but were introduced to the Middle East, India, and finally China by 850 AD. These were used as medicinal plants in Ancient Greece and Medieval Europe. Their popularity declined in Europe following the introduction of spinach.
• B. v. ssp. v. convar. cicla. var. cicla (spinach beet) - This variety is widely cultivated for its leaves, which are usually cooked like spinach. It can be found in many grocery stores around the world.
• B. v. ssp. v. convar. cicla. var. flaviscens (chard) - Chard is grown for its leaves, which have thick and fleshy midribs that are used as a vegetable. Some cultivars are also grown ornamentally for their coloured midribs. The thickened midribs are thought to have arisen from the spinach beet by mutation.
• B. v. ssp. vulgaris convar. vulgaris (tuberous beets) - This grouping contains all beets grown for their thickend tubers rather than their leaves.
• B. v. ssp. v. convar. vulgaris var. crassa (mangelwurzel) - This variety was developed in the 1700s for its tubers for use as a fodder crop
• B. v. ssp. v. convar. vulgaris var. altissima (sugar beet) - The sugar beet is a major commercial crop due to its high concentrations of sucrose, which is extracted to produce table sugar. It was developed in Germany in the late 18th century after the roots of beets were found to contain sugar in 1747.
• B. v. ssp. v. convar. vulgaris var. vulgaris (garden beet) - This is the red root vegetable that is most typically associated with the word 'beet'. It is especially popular in Eastern Europe where it is the main ingredient of borscht.