Jane Says: Let’s Settle This Yam-Sweet Potato Confusion Once and For All

Though the term ‘yam’ is thrown around with abandon, there’s a big difference between the white starchy tuber and sweet potatoes.
What you're looking at is not a yam. (Photo: Getty Images)
Oct 10, 2012· 3 MIN READ
Jane Lear is a regular contributor to TakePart and the executive editor of CURED, a magazine devoted to the art and craft of food preservation. She was on staff at 'Gourmet' for almost 20 years.

“We hear over and over that America doesn’t have true yams, yet some sort of tuber continues to be marketed as yams. What’s the truth?” —Betsey Porter

“How do you make good—and actually crispy—baked sweet potato fries? Mine never come out crispy enough.” —Meagan Freeman (seconded by David Parsons)

The true yam, or ñame (pronounced “ny-AH-may”), is a starchy tuber that originated in the tropical regions of both the Old World and (to a far lesser extent) the New. Extrapolate from this and you may presume that it was brought to the North American mainland by slaves, along with other staples like okra, pigeon peas, and sorghum.

You would be wrong. Enslaved Africans didn’t have a chance to sew seeds in the hems of their clothes, like many immigrants did. They were naked, and in chains. So yams were brought to North America not by slaves, but by European slave traders, who used yams—along with okra, pigeon peas, sorghum, plantains, taro, and other African staples—to provision their cargo on the Middle Passage (their route across the Atlantic), as well as in the holding facilities in the Caribbean.

There are about 60 edible species of yam, and you will find a number of them in African, Caribbean, Philippine, and Latin groceries. One cultivar you may see is Dioscorea rotundata (known as the African, Guinea, or white yam), which can weigh a good three pounds or more. It’s very similar to a boiling potato in texture; waxy and dense, it’s usually pounded into a stiff dough, then neatly mounded and eaten as fufu, with spicy stews. Another cultivar, Dioscorea trifida, originated in South America and is often called the cushcush or mapuey yam. It’s prized for its wonderfully dry, light, fluffy texture when cooked. As far as flavor goes, generally speaking, yams range from mildly sweet and delicate to bland.

In the plantation era, yams quickly became important to the food supply of the Caribbean. They grow prolifically and underground—the tubers can survive a tropical storm or hurricane, unlike a grain crop—they store well, and they are versatile in the kitchen. But climate prevented yams from ever flourishing on the North American mainland.

And not one of them is remotely related to the sweet potato (Ipomoea batatas), a member of the morning glory family and a New World native introduced to the Old through the Columbian Exchange.

Why the confusion? The clearest explanation—partly historical, partly recent—comes from Elizabeth Schneider in her 2001 reference work, Vegetables From Amaranth to Zucchini, an instant classic if there ever was one. “The English word ‘yam,’ surmised to be of West African origin,” she writes, “came via a word recorded by Portuguese slave traders, inhame (pronounced eenyam). This word was also used in the American South, but erroneously applied to the sweet potato.” Whoops.

Schneider goes on to explain that in the 1930s (yep, in the grand sweep of history, that is recent), promoters of Louisiana-grown sweet potatoes hit on the word yam for a campaign to set apart their product from the drier, paler sweets grown in other states, including Virginia, Maryland, and New Jersey. Hmm. Kinda puts the whole concept of branding—and sourcing—into perspective, doesn’t it?

Digression: Not only are sweet potatoes not yams, they’re not true potatoes (Solanum tuberosum), either. I’ll spare you the linguistic slip-slide from batata to patata and potato—or pa-tah-to—oh, let’s call the whole thing off. Or stick to Latin.

One similarity that sweets share with yams is their great variability. What you’ll most commonly find at U.S. supermarkets, though, are orange-fleshed cultivars like Beauregard, Jewel, and Garnet.

Okay, now let’s get to the nitty-gritty: baked sweet potato fries. I know many people think of sweets as a healthier substitute for regular potatoes, and you expect them to behave the same way in the kitchen.

They don’t. Because of the different starch, sugar, and water content, things do not play out the same way. And you also have to understand that the moisture in sweet potatoes varies with the specific cultivar, how it was stored, and the length of time after harvest. In general, though, if you are hell-bent on crisp oven-baked fries, you need some sort of coating. Some people have good luck with cornstarch. But I learned from my former Gourmet colleague Gina Marie Miraglia Eriquez that if you toss the fries with an egg white, then spread them on a baking sheet in a single layer and bake at 450°, they crisp up beautifully. Gina adds, “Also, when I am lazy, I don't peel them but just toss with olive oil and salt and roast at 450° (parchment helps, too), they do come out pretty crispy.”

Or, you could simply work with the vegetable’s own natural inclination toward tenderness. Cut the sweets into wedges and peel or not, depending on your preference. Toss them with olive oil, salt, pepper, and maybe a little cumin. Spread them on a rimmed baking sheet lined with parchment (for ease of cleanup) and bake in a 400° oven until they start to smell good. Turn them over and continue to bake until they’re golden brown and sort of crisp on the outside and meltingly tender within. If you seasoned them with cumin, spritz them with a little fresh lime juice before serving. Yum.