The sweet potato (Ipomoea batatas) is a creeping, vine-like plant that is cultivated in tropical climates for its starchy, nutritious tubers. The sweet potato is in the morning glory family (Convolvulaceae). The sweet potato is sometimes referred to as a yam, but it is quite different from the true yam (Dioscorea batatas), which is another species of tropical root-crop.
The sweet potato is a perennial, trailing vine that develops tubers at the ends of adventitious roots. Sweet potatoes are easily propagated vegetatively, by planting small pieces of roots or vine cuttings.
Although sweet potatoes are not consumed in large quantities in North America or Europe, they are a very important crop in the tropics. The global production of sweet potatoes ranks this plant with the eight most important foods grown by people in terms of the annual production of edible biomass (about 127,000,000 tons [140,000,000 mt] per year).
Sweet potatoes have an ancient history of cultivation as a food crop. Archaeological evidence suggests that sweet potatoes may have been grown in Peru for as long as 5,000 years. This crop is known to have been cultivated in the tropical Americas, Southeast Asia, and Polynesia at the time of the first visits to these regions by Europeans. Many botanists believe that the sweet potato originated in Central America or northern South America, and was then somehow transported to Asia during prehistoric times. This dispersal may have happened by now-forgotten, trans-Pacific trade or migration voyages, or possibly by seed capsules floating across the ocean.
There are many varieties of sweet potatoes, but these can be categorized into two broad groups. One group has moist, sweet tubers with an orange-colored interior—this is the type most commonly found in markets in North America. The other, more diverse group of sweet potatoes has a drier and mealier tuber, with a yellow, white, or red-colored interior, and is most extensively grown and eaten throughout the tropics.
Sweet potatoes are a valuable source of carbohydrate, beta-carotene, and fiber, containing as much as 5% protein. However, a diet rich in sweet potatoes must be balanced with other foods, mostly to ensure an adequate intake of proteins, and a balance of essential amino acids. Sweet potatoes can be eaten after boiling or roasting, or they can be manufactured into a flour, or used to make a product known as Brazilian arrowroot, and sometimes fermented into alcohol. Sweet potatoes are also fed to livestock, as are the vines and foliage of the plant. Because the tubers are rather moist, sweet potatoes spoil relatively easily, and crops do not always store well.