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Do you ever find yourself loitering in the produce aisle, internally debating the merits of yams versus sweet potatoes? At many grocery stores, they often look identical, but I’ve found that “yams” can be as low as 79 cents per pound, while “sweet potatoes” cost $2.49 per pound. So, what’s the difference between a sweet potato and a yam? At most markets: absolutely nothing. It’s all a facade! “Most of the so-called yams you see in American grocery stores are actually orange-fleshed sweet potatoes,” explains Mary-Frances Heck, a former BA staffer and the author of Sweet Potatoes. The reason for the name mix-up, she explains, is because Louisiana sweet potato growers in the 1930s marketed a new breed of orange-fleshed sweet potatoes as “yams” to distinguish their crop from other states’ produce—and it stuck.
The word yam is derived from nyam, nyami, or nyambi, verbs of various African dialects meaning either “to taste” or “to eat.” The prevailing theory is that enslaved Africans applied these terms over time to the sweet potatoes available in the Americas, which took the place in their diet of the staple root vegetable grown in much of West Africa.
So, what are yams?
True yams are part of an entirely different genus (Dioscorea; sweet potatoes belong to Ipomoea in the morning glory family) and are more akin to yuca in texture and flavor. Yams are commonly used in Caribbean and West African cooking and can grow as long and thick as an adult arm. They have bumpy, tough gray-brown skin (that looks almost like the bark of a tree and must be peeled away with a knife as it’s far too tough for a vegetable peeler). Most varieties aren’t sweet. The most common yams have starchy white flesh (though some reddish, yellow, and purple cultivars exist, such as ube, a.k.a. the purple yams popular in Filipino cooking) and can be more rightly compared to the texture and flavor of white russet potatoes, but with more fiber and complex carbs. Neutral flavored yams are often boiled or steamed to serve alongside hearty braised meats; the cooked flesh may be pounded into fufu or swallow, a starchy paste eaten in many cuisines of the African diaspora.
To complicate things further, there are a handful of sweet potato varieties in a wide range of colors, including orange, white, and purple. We had Heck break down the differences for us.
Varieties of sweet potatoes:
This is the most common type of sweet potato found in the United States. These are the ones you roast for meal prep, purée for Thanksgiving sweet potato pie or marshmallow-topped sweet potato casserole, and (yes) dice into candied yams. They also make excellent fries and chips and make an excellent easy lunch or side dish when simply steamed. They’re versatile, widely available, and the varietals within the orange-fleshed potatoes are all “pretty much interchangeable,” says Heck. She notes there will be “subtle differences in flavor, sweetness, and moisture” between Beauregard (brown skin, more deeply sweet, grown in Louisiana), Garnet (red skin, more like pumpkin flavor), and Jewel (coppery-orange skin, mildly sweet and earthy, California-grown).
White sweet potatoes—i.e., sweet potatoes with white flesh—are loaded with some of the same fiber and vitamins that orange sweet potatoes have (though not as much beta-carotene). They may look identical to Garnet yams on the outside, or (as in Japanese sweet potatoes) they may have ruby-colored skins. Sometimes they’ll even fool you into thinking they’re a regular old russet. Since these tubers tend to be a little drier in texture than orange-fleshed varieties, Heck suggests using them for gnocchi so you can control the amount of moisture in the dough. For non-pasta applications, Heck says they go well with bright, acidic sauces like chimichurri. The texture is more toothsome than mushy when roasted, but if you braise them low and slow, they end up being silky yet still hold their shape.
Purple sweet potatoes have super amped-up anthocyanin like blueberries, which are great for both color and antioxidants. The term may apply to sweet potatoes with purple skin and creamy white flesh, ones with white skin and deep purple flesh, or varieties in which both the skin and flesh are shades of purple. But don’t confuse them with Peruvian purple potatoes—the vividly colored spuds from South America are savory, not sweet.
The North Carolina-grown Stokes varietal is the most popular (with a sweet chestnut flavor), but you can sometimes find Hawaiian Okinawan potatoes, with purple-speckled flesh, that are best when boiled whole. Heck suggests roasting, sautéing, or frying purple sweet potatoes to prevent the color from bleeding out when cooking. You could also blend them up into a stunningly hued sweet potato soup. One of Heck’s favorite ways to eat them is to top them with sambal butter. You can make sambal paste with chiles, garlic, ginger, lemongrass, lime zest, and salt, or just mix 1 Tbsp. sambal oelek with 1 stick butter. As it melts into your potato, all your produce aisle quandaries may melt away too.
