Like strangers on the same page of a phone book, sweet potatoes and white potatoes share nothing more than a common last name. Both potatoes are, of course, plants. But sweet potatoes belong to the morning glory family, while white potatoes belong to the nightshade family – sometimes called the potato family. More to the point, sweet potatoes are roots of the dicotyledonous plant; white potatoes are underground stems (tubers) of the potato plant.
Yams, meanwhile, belong to the yam family, and are tubers of the monocotyledon plant. But even though they are tubers, yams have a closer lineage to lilies, than to either the white potato or the sweet potato. The confusion over yams …
