Taste like candy; look like potatoes.
Let’s get one thing straight: sweet potatoes and yams are not the same vegetable. Unless you’re shopping at an international market, you’re probably buying a sweet potato, not a yam.
Sweet potatoes are native to the tropical Americas. They were domesticated at least 5,000 years ago, when the sweet root served as a staple crop for Incan and pre-Incan cultures. Today, sweet potatoes are a widely diverse crop, ranging from yellow to red in appearance and firm or soft in texture. Some sweet potato varieties will remain firm when cooked; others will soften. These softening varieties provoke the yam v. sweet potato confusion, since yams (native to parts of Africa and Asia, where 95+% are grown today) also soften when cooked. African slaves, who noted the similarity between the newly developed soft sweet potatoes and their native yams, began calling them yams to differentiate the two varieties.
Sweet potatoes are also not potatoes, though the two are distantly related. Potatoes are in the nightshade family, while sweet potatoes, with their creeping, flowering vines, are part of the morning glory family.
But we don’t have to define sweet potatoes just for what they’re not. They are an oh-so-easy manifestation of the sweet/savory combo: just roast or bake them with a little butter. They are nutrient-dense, a great source of vitamin A and beta-carotene. The Center for Science in the Public Interest even rated sweet potatoes as the top nutritional vegetable. Be sure to eat the skins too — they are packed in fiber.
Sweet potatoes are even grown as ornamental plants, with beautiful small flowers, and the tuber has been used traditionally to make red dye.
When first harvested, sweet potatoes lack their distinctive sweet taste. They must be cured at high temperature and humidity for about a week, then stored at cooler temperatures for 6-8 weeks. This processing helps the sweet potatoes develop sugar-creating enzymes.
Sweet potatoes can store for months in the right conditions. Keep them in a dark, cool location, but not so cool as the vegetable drawer in your refrigerator. Around 55 degrees is better.