Sweet Potato (Kumara)
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The sweet potato (Ipomoea batatas), commonly called a yam in parts of the United States (especially in the southern and western portions of the country; this terminology causes some confusion with true yams), is a crop plant whose large, starchy, sweet tasting tuberous roots are an important root vegetable. The young leaves and shoots are sometimes eaten as greens. The sweet potato is only distantly related to the potato (Solanum tuberosum). It is even more distantly related to the true yam (Dioscorea species) which is native to Africa and Asia.
The genus Ipomoea that contains the sweet potato also includes several garden flowers called morning glories, though that term is not usually extended to Ipomoea batatas. Some cultivars of Ipomoea batatas are grown as ornamental plants.
This plant is a herbaceous perennial vine, bearing alternate heart-shaped or palmately lobed leaves and medium-sized sympetalous flowers. The edible tuberous root is long and tapered, with a smooth skin whose color ranges between red, purple, brown and white. Its flesh ranges from white through yellow, orange, and purple.
Sweet potatoes are native to the tropical parts of the Americas, and were domesticated there at least 5000 years ago.   They spread very early throughout the region, including the Caribbean. They were also known before western exploration in Polynesia. How exactly they arrived there is the subject of a fierce debate which involves archaeological, linguistic and genetic evidence.
Sweet potatoes are now cultivated throughout tropical and warm temperate regions wherever there is sufficient water to support their growth.
According to 2004 FAO statistics world production is 127,000,000 tons . The majority comes from China with a production of 105,000,000 tonnes from 49,000 km². About half of the Chinese crop is used for livestock feed .