What Kind of Yam is a Sweet Potato? Separating Botanical Fact from Marketing Fiction

January 12, 2026 •

4 min read

Despite a common misconception stemming from 1930s U.S. marketing, a sweet potato is not any kind of yam at all; they are entirely different plants from separate families. This article directly addresses the question, 'What kind of yam is a sweet potato?', by exploring their botanical differences and clearing up the decades-old confusion that persists today.

Quick Summary

Sweet potatoes and true yams are distinct root vegetables from different plant families. Their names were confused historically due to U.S. marketing and cultural naming practices, but they differ in taste, texture, and origin.

Key Points

No Relation: Sweet potatoes belong to the morning glory family (Convolvulaceae), while true yams are in the lily family (Dioscoreaceae).
Marketing Mix-Up: The term "yam" was historically used in the U.S. to market softer, orange-fleshed sweet potatoes, causing widespread confusion.
Distinct Characteristics: True yams have rough, bark-like skin and starchy, dry flesh, unlike the smoother-skinned, sweeter, and moister sweet potato.
Separate Origins: Sweet potatoes are native to the Americas, whereas true yams originate from Africa and Asia.
USDA Mandate: U.S. regulations require labels featuring "yam" to also display "sweet potato" for clarity.
Nutritional Benefits: While both are nutritious, sweet potatoes are notably richer in Vitamin A.
Source for Yams: If you want true yams, you must shop at international or ethnic specialty markets.

The Fundamental Difference: Sweet Potatoes Are Not Yams

Many Americans grow up using the terms "sweet potato" and "yam" interchangeably, but this is a botanical error. The food most commonly referred to as a yam in U.S. supermarkets is actually a soft, moist variety of sweet potato. True yams and sweet potatoes belong to entirely different plant families and are not related, much like a carrot is not a type of turnip. This widespread mix-up is primarily a product of marketing history in the United States, which started in the 1930s when growers began labeling orange-fleshed sweet potatoes as "yams" to set them apart from the paler, firmer varieties already on the market.

A Look at Their Taxonomy

To understand the vast difference, one must look at the scientific classification of each plant:

Sweet Potato (Ipomoea batatas): This plant is a dicot and is part of the morning glory family, Convolvulaceae. Its edible part is a storage root, not a true tuber like a potato. Sweet potatoes are native to Central and South America.
True Yam (Dioscorea spp.): This is a monocot, belonging to the lily family, Dioscoreaceae. The edible portion is a stem tuber. True yams originate from Africa and Asia and are a staple crop in many tropical regions.

The History Behind the Naming Confusion

The story of how sweet potatoes came to be misidentified as yams is twofold. First, when softer, orange-fleshed sweet potato varieties were introduced to American markets, growers needed a way to distinguish them from the firmer, drier, white-fleshed ones. They borrowed the term "yam," which had been used by enslaved West Africans to refer to the local American sweet potato because it reminded them of the African yams they knew. Secondly, the name stuck, and today the U.S. Department of Agriculture requires any label featuring the term "yam" to also be accompanied by "sweet potato" to prevent confusion.

How to Tell the Difference Between a Sweet Potato and a Yam

While the market labeling can be misleading, there are several key physical differences between a sweet potato and a true yam. Knowing these can help you select the right ingredient for your recipe.

Appearance: Skin and Shape

Sweet Potato: Has smooth, thin skin that can range in color from reddish-brown, copper, or purple to white. It has tapered, oblong ends.
True Yam: Features rough, dark brown, and scaly skin, often compared to tree bark, that is much thicker than a sweet potato's. True yams can be cylindrical and grow much larger, sometimes over five feet long.

Texture and Flavor Profiles

Sweet Potato: The flesh is typically moist and sweeter than a yam's, especially the common orange varieties. The texture can be soft and creamy when cooked.
True Yam: The flesh is drier, starchier, and often has a more neutral, earthy flavor. The color can be white, purple, or reddish, depending on the variety.

Where to Find True Yams

For most U.S. shoppers, the vegetables labeled as "yams" at the local supermarket are simply orange-fleshed sweet potatoes. If you're looking for true yams, you'll likely need to visit international or ethnic food markets that specialize in African, Caribbean, or Latin American cuisine.

Culinary Uses and Preparation

Given their different textures and flavors, sweet potatoes and true yams are best used in specific culinary applications. The sweet, moist properties of a sweet potato make it ideal for dishes where its sweetness can shine, while the starchy, neutral nature of a true yam allows it to be used more like a standard potato.

Sweet Potato Preparation: Baked, mashed, fried into chips or fries, or used in desserts like pies and casseroles. Roasting can caramelize its natural sugars for enhanced sweetness.
True Yam Preparation: Boiled, roasted, or fried. In West African cuisine, yams are often pounded into a paste called fufu or used in stews and soups.

Comparison: Sweet Potato vs. True Yam


Feature	Sweet Potato (Ipomoea batatas)	True Yam (Dioscorea spp.)
Plant Family	Morning Glory (Convolvulaceae)	Lily (Dioscoreaceae)
Origin	Central & South America	Africa & Asia
Skin	Smooth, thin, reddish-brown, copper, or white	Rough, thick, bark-like, dark brown
Flesh	Moist, sweet, orange, white, or purple	Dry, starchy, white, purple, or reddish
Flavor	Naturally sweet, can be nutty	Neutral, earthy, less sweet
Common U.S. Source	Supermarkets, often mislabeled as "yams"	International or ethnic food markets
Nutritional Highlight	Rich in Vitamin A and Beta-Carotene	Good source of Vitamin C and Folate

Conclusion: The Final Word on Sweet Potatoes and Yams

The most important takeaway is that the common culinary confusion is purely a North American phenomenon stemming from historical marketing and cultural naming practices. What you find in the typical U.S. grocery store and call a yam is, in fact, a sweet potato. True yams are a different vegetable entirely, with unique physical characteristics and culinary applications. By understanding their botanical differences and origins, you can make more informed choices about which root vegetable is right for your next meal.

For further reading on the agricultural details and nutritional composition, explore information from authoritative sources like the Library of Congress.

Frequently Asked Questions

No, a sweet potato is not a type of yam. They are from different botanical families; sweet potatoes are in the morning glory family, while true yams are in the lily family.

Sweet potatoes are sometimes called yams due to historical U.S. marketing practices that used the name to distinguish orange-fleshed varieties, and because enslaved Africans used the term for sweet potatoes that reminded them of native African yams.

True yams are typically sold in international, specialty, or ethnic food markets. The vegetables labeled 'yams' in most U.S. supermarkets are actually sweet potatoes.

You can tell the difference by looking at the skin and flesh. True yams have rough, bark-like skin and starchy, dry flesh, while sweet potatoes have smoother skin and sweeter, moister flesh.

No, the vegetables sold as canned 'yams' in the U.S. are almost always a type of sweet potato. The USDA requires these products to be dual-labeled as 'sweet potato'.

Both are healthy, but sweet potatoes generally contain more vitamin A and beta-carotene, and slightly fewer calories than yams.

Yes, their flavors differ significantly. Sweet potatoes are naturally sweet and moist, while true yams are starchier, drier, and have a more neutral, earthy flavor.