<P> The sweet potato (Ipomoea batatas) is a dicotyledonous plant that belongs to the bindweed or morning glory family, Convolvulaceae . Its large, starchy, sweet - tasting, tuberous roots are a root vegetable . The young leaves and shoots are sometimes eaten as greens . The sweet potato is only distantly related to the potato (Solanum tuberosum) and does not belong to the nightshade family, Solanaceae, but both families belong to the same taxonomic order, the Solanales . </P> <P> The 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 yellow, orange, red, brown, purple, and beige . Its flesh ranges from beige through white, red, pink, violet, yellow, orange, and purple . Sweet potato cultivars with white or pale yellow flesh are less sweet and moist than those with red, pink or orange flesh . </P> <P> Ipomoea batatas is native to the tropical regions in the Americas . 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 (e.g., I. aquatica "kangkong"), but many are poisonous . 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 under the name tuberous morning glory, used in a horticultural context . </P> <P> Although the soft, orange sweet potato is often called a "yam" in parts of North America, the sweet potato is botanically very distinct from a genuine yam (Dioscorea), which is native to Africa and Asia and belongs to the monocot family Dioscoreaceae . To add to the confusion, a different crop plant, the oca (Oxalis tuberosa, a species of wood sorrel), is called a "yam" in many parts of Polynesia, including New Zealand . </P>

When did sweet potatoes come to north america
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