If you’re in the U.S., chances are that the “yams” you eat at Thanksgiving are actually sweet potatoes. Shocked? It’s true: yams and sweet potatoes are totally different plants and are not even closely related. In fact, these tasty starchy veggies are actually in two different plant families entirely!
Yams are members of the genus Dioscorea and are in their own special family, Dioscoreaceae. They are tubers, like potatoes, and are mostly cultivated in tropical parts of the world. A number of different yam species are grown for food, and the large tubers range in color from white to yellow, pink, or purple! The skin is typically brown and rough, like tree bark. They vary in taste from sweet to bitter to tasteless and tend to be a bit on the dry starchy side.
Sweet potatoes, on the other hand, come from the species Ipomoea batatas, in the morning glory family, Convolvulaceae. The edible roots are indeed true roots, like carrots or beets, and are typically orange or white inside, though the smooth skin can be a variety of colors. Sweet potatoes are widely grown in the southern United States and are common in tropical America and parts of the Pacific. They are typically sweet tasting and moist.
So, how did the confusion arise? It seems that American slaves referred to the soft orange-fleshed sweet potatoes as “yams” because of their similarity to the true yams they knew from Africa. Growers began using this name to distinguish them from the firm white-fleshed varieties of sweet potatoes, and the name stuck. Although the U.S. Department of Agriculture requires labels with the term yam to be accompanied by the term sweet potato when applicable, many Americans are unaware that true yams are different from sweet potatoes.
Before you reach for the candied yams this Thanksgiving, there's something you need to know. They're not actually yams! All this time, many Americans have been making the mistake of calling sweet potatoes "yams." But there's actually a difference. It turns out sweet potatoes and yams are not even related. They are two different species of root vegetable with very different backgrounds and uses.
So why the confusion? The U.S. government has perpetuated the error of labeling sweet potatoes "yams." In most cases sweet potatoes are labeled with both terms, which just adds to the confusion. Since there are two types of sweet potatoes, one with creamy white flesh and one with orange, the USDA labels the orange-fleshed ones "yams" to distinguish them from the paler variety. Ok, so that sort of makes sense. But why call the orange-fleshed ones "yams" in the first place? So to understand the difference between yams and sweet potatoes, we have to dig a little deeper (tuber pun intended).
Sweet potatoes (Ipomoea batatas) come in two main varieties here in the States. One has a golden skin with creamy white flesh and a crumbly texture. The other has a copper skin with an orange flesh that is sweet and soft. All sweet potato varieties generally have the same shape and size -- they are tapered at the ends and much smaller than the aforementioned yams.
Americans have been calling the orange-fleshed variety of sweet potatoes "yams" since colonial times when Africans saw familiarities in them to the tuberous variety. The USDA decided to label them as "yams" to differentiate the two varieties. Both varieties of sweet potato, including "yams" can be widely found in supermarket.
Yams (family Dioscoreaceae) are native to Africa and Asia and other tropical regions. Yams are starchy tubers that have an almost black bark-like skin and white, purple or reddish flesh and come in many varieties. The tubers can be as small as regular potatoes or grow upwards of five feet long.
The word yam comes from an African word, which means "to eat." The yam holds great importance as a foodstuff because it keeps for a long time in storage and is very valuable during the wet season, when food is scarce. For eating, yams are typically peeled, boiled and mashed or dried and ground into a powder that can be cooked into a porridge. Yams can be found in international markets, such as those that specialize in Caribbean foods.
For more information on sweet potatoes, visit the North Carolina Sweet Potato Commission.
For more on the nutritional value of sweet potatoes vs. yams, visit Livestrong.com.
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So, the big question is: What do you call sweet potatoes?