Yams are often mistakenly called sweet potatoes and vice versa, but these are actually two different vegetables. A true yam is the tuber of a tropical vine that can grow over seven feet in length, and it's not even distantly related to the sweet potato. Yams are a popular vegetable in Latin American and Caribbean markets, but the genuine article can be difficult to find in U.S. stores.
The yam's botanical name is dioscorea batatas. Depending on country and region, it may also be called a boniato, njam, nyami, djambi, yamswurzel, ñame or igname de chine.
How to Identify a Real Yam
True yams are indigenous to Africa and Asia, with most grown in Africa, but there are over 150 varieties of yams available worldwide. Yams are mostly sold in chunks, sealed in plastic wrap—if you can even find them in the U.S. at all. They can reach up to 150 pounds, but they can also be as small as your average spud. True yams have rough, dark skin, and their flesh can range from white to a reddish color, but it's usually white.
Although you might find canned vegetables labeled as yams, these probably aren't true yams. Even the "yams" found in fresh produce sections of grocery stores are rarely real yams. They're soft sweet potatoes, which are different from firm sweet potatoes. U.S. grocers began selling these homegrown soft potatoes as yams hundreds of years ago in an effort to differentiate them from the firm sweet potatoes people had been buying for years. The FDA has never gotten involved in this case of mistaken identity to sort out the discrepancy.
Real yams are imported. Your best chance of finding the real deal is at specialty and ethnic markets. Choose yams with unblemished, tight, unwrinkled skins and firm flesh. And yes, like just about everything else these days, you can buy real yams online.
What Does a Yam Taste Like?
Yams tended to be drier than sweet potatoes and they're starchier. They're often served boiled and sprinkled with palm oil in their native Africa, but they can also be roasted, fried, grilled, or baked. Unlike sweet potatoes, yams are toxic if they're eaten raw, but they're perfectly safe when cooked. True yams can generally be substituted in any sweet potato recipe.
Store fresh, uncooked yams in a cool, dark, dry area for up to two weeks. Do not refrigerate them. Cooked yams can be kept refrigerated for two to three days. Pack them in an airtight container if you want to freeze them, leaving about a half inch of headroom. You can safely freeze yams for 10 to 12 months at 0 F.
True yams don't contain as much Vitamin A and C as sweet potatoes, but they're high in potassium and fiber.