The sweet potato is a dicotyledonous plant that belongs to the family Convolvulaceae. Its large, starchy, sweet tasting tuberous roots are an important root vegetable (Purseglove, 1991; Woolfe, 1992). The young leaves and shoots are sometimes eaten as greens. Of the approximately 50 genera and more than 1,000 species of Convolvulaceae, I. batatas is the only crop plant of major importance – some others are used locally, but many are actually poisonous.
The sweet potato is only distantly related to the potato (Solanum tuberosum). The softer, orange variety is commonly marketed as a "yam" in parts of North America, a practice intended to differentiate it from the firmer, white variety. The sweet potato is very distinct from the actual yam, which is native to Africa and Asia and belong to the monocot family Dioscoreaceae. To prevent confusion, the United States Department of Agriculture requires that sweet potatoes labeled as "yams" also be labeled as "sweet potatoes".
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; the slightly ambiguous name "tuberous morning glory" may be used in a horticultural context.
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 colour ranges between red, purple, brown and white. Its flesh ranges from white through yellow, orange, and purple.