Although common marketing practice in North America, calling sweet potatoes yams is a misnomer.
The two plants are botanically very different. Many plants in the sweet potato family, Convolvulaceae, are actually poisonous and only one species is widely used commerically. Yams, on the other hand, yield from a variety of perennial vines.
Yams are an important crop in Asia and Africa while sweet potatoes - distantly related to potatoes by the way - have been cultivated in Central and South America for thousands of years.
(Source: Wikipedia)




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