Sweet potato
Family Convolvulaceae
Ipomoea batatas, the sweet potato (I. batatas 1), is a perennial herb with twining stems (I. batatas 2), 1-5 m long, with latex in all parts. The simple leaves are very variable in shape, entire to deeply lobed, depending on age. The flowers (I. batatas 3) are borne solitary or in axillary clusters, with a 5-lobed calyx and a funnel-shaped corolla, 3-4 cm in diameter and 3-5 cm long, purplish in colour with deeper colour in throat; 5 stamens and ovary surrounded by an orange nectary. The fruit is a capsule containing black seeds, but in the tropics propagation is always by stem cuttings.
The edible root tubers are very variable in shape (I. batatas 4), (I. batatas 5), size (I. batatas 6), (I. batatas 7), and colour (I. batatas 8). The many varieties can also be divided in those with dry mealy flesh and those with moist soft flesh. They are an important source of food in many tropical countries, containing up to 25% starch.
Distribution
The cultivated sweet potato is not known in a wild state, but it is almost certain that it originated in tropical America. In pre-Columbian time, sweet potatoes were grown in Mexico, the West Indies and parts of Central and South America. Columbus took it to Spain in 1492, nearly 80 years before the potato reached Europe. The Spaniards took it from Mexico to the Philippines, and the Portuguese introduced it in Africa and Asia. The Chinese took it from the Philippines in 1594 and it reached Japan in 1698. Halfway the 17th century early colonists took it to northern America. By the mid-19th century it was well established in Africa.
Use
Sweet potatoes are usually eaten boiled or baked. Besides starch, they contain a small amount of protein and some sugar. They are also used for making flour and as a source of starch, glucose and alcohol. Vines and leaves are used as a fodder.