Myth-busting today: we don’t have yams here in North America, we have sweet potatoes. Ignore the signs at your supermarket that separate the potatoes into two sections, you probably won’t see a true yam in a regular American supermarket – though you may find some in an ethnic grocery alongside taro corms and other tropical tubers.
Sweet potatoes are the large, edible storage roots of the morning glory family (Convolvulaceae), which grows primarily in South America. Each plant produces 4-10 potatoes that have smooth, thin skins and flesh that varies from orange to pale yellow (though there is a purple variety as well). Sweet potatoes are high in beta caratene, and the flesh is moist and sweet (go figure) rather than starchy. The potatoes are typically short and blunt, tapered at the ends. There are hundreds of varieties of sweet potatoes, but they all have eyes.
Yams, on the other hand, are tubers of a tropical perennial Dioscoreaceae vine and are common in places like Nigeria, Brazil, and Ghana. The tubers are high in vitamin B6 and potassium, starchy, dry, and covered with thick, rough, hairy skin that is difficult to peel. They can grow up to 8 feet long (!) and weigh over 150 pounds. The flesh of true yams varies from white or yellow to pink or purple (but not orange), and they don’t have eyes.