Aren't yams and sweet potatoes the same thing? Nope. Here's everything you need to know about the difference between the two, and why we've been confusing one for the other.
Sweet Potato and a Yam
Credit: Getty Images

For many of us, the terms sweet potato and yam may be interchangeable. The truth is, generations of Americans have been getting it wrong. Sweet potatoes and yams are not the same. They are two separate foods that aren't even from the same family. We'll tell you when the confusion exactly began, and explain, once and for all, what the difference is between sweet potatoes and yams.

Why the Confusion? 

If yams and sweet potatoes are different from each other, what caused their names to be used interchangeably? The answer: marketing. In the 1930s, a new sweet potato variety that was larger and sweeter, with soft orange flesh, was cultivated by Julian C. Miller at the Louisiana Sate University Agricultural Center. In order to differentiate it from the sweet potatoes that already existed (smaller, drier and with white or yellowish flesh), sweet potato growers decided to call the new variety a yam—a word that is rooted in the West African words nyam, nyami or enyame, which mean "to eat." Communities of enslaved Africans were the first to refer to the sweet potato as a yam, as it reminded them of the ones they ate in Africa. 

Today, USDA regulations require yam labels to be followed by the term "sweet potatoes" when they are technically (and biologically) not yams.

So, What Is a Yam?

A yam is the modified stem or tuber of a tropical vine called Dioscorea batatas. Although they may look similar to sweet potatoes, they are an entirely different species (yams belong to the Dioscoreaceae family and are related to grasses and lilies, and sweet potatoes belong to the morning glory family) and not even remotely related. Yams grow in subtropical and tropical climates like Africa, South America and the Caribbean and are commonly found in cuisines from those areas. There are more than 150 different yam varieties in the world.

Unlike sweet potatoes, most yams are starchy and not very sweet—if anything they taste more like potatoes or yuca (also know as cassava or manioc) than sweet potatoes. They have a more cylindrical shape with rough, scaly skin that's brown and almost tree-bark-like in appearance. Their flesh can range in color from off-white to red or purple, while their flavor is mostly mild and neutral. They are high in carbohydrates with a decent amount of fiber, vitamin C, vitamin B6, potassium and manganese.

Real yams are not widely available in the U.S. They are usually found at grocery stores that specialize in Latin American, Caribbean, Southeast Asian and African products.

What Is a Sweet Potato?

A sweet potato is the storage root of Ipomoea batatas. They grow in warm, temperate climates as well as in tropical regions. They are native to the Americas but grown in many parts of the world. Thousands of different varieties exist today.

Compared to yams, sweet potatoes are shorter. They usually have a bulging middle with ends that taper to a point. In the U.S., sweet potatoes are generally categorized into two types: firm and soft. Firm sweet potatoes usually have generally pale skin and flesh and are drier and less sweet. Soft sweet potatoes are usually darker all around and are moister and sweeter. These orange-fleshed varieties are the ones most commonly mistaken for "yams." Sweet potatoes grown stateside can have thinner skin that ranges in color from yellow to red to purple with flesh that's pale yellow, orange or purple.

Sweet potatoes have a similar nutritional profile to yams, however, they are higher in sugar, vitamin A and beta carotene.

Although peak sweet potato season is in the winter, they can be found year-round at grocery stores in the U.S. Some of the most popular varieties are Hannah (light brown skin and off-white flesh), Jewel (red-brown skin and dark-orange flesh), Garnet (red-purple skin and orange flesh) and Beauregard (dusty-red skin and orange flesh).

Uses for Yams vs. Sweet Potatoes

Yams and sweet potatoes can both be prepared by roasting, steaming, boiling or frying. Substituting real yams in a sweet potato dish would be like using potatoes instead of sweet potatoes in the recipe—it would work, but the end result would taste very different.

We recommend sticking with soft sweet potato varieties for traditional Thanksgiving dishes like Candied Sweet Potatoes and Smashed Spiced Sweet Potatoes, and in dishes where their natural sweetness is key, like these Sweet Potato Waffles. If you're lucky enough to get your hands on some real, fresh yams, try boiling, roasting or frying them.

Bottom Line

A yam is a tuber. A sweet potato is a root. Yams tend to be more cylindrical and have scaly, bark-like skin. Sweet potatoes tend to have a more tapered shape and may be firm or soft with thinner skin. Generally, sweet potatoes taste sweeter than yams. You will more readily encounter sweet potatoes during your regular grocery run, but if you spot a yam, which may be labeled "sweet potato," you'll know the truth.