Here’s the first curveball: true yams and sweet potatoes aren’t even related. Botanically speaking, sweet potatoes are from the morning glory family, while yams are from a totally different plant family, native to Africa and Asia.
The confusion? It’s all America’s fault. In the 1930s, Louisiana farmers started marketing a soft, orange-fleshed sweet potato as a “yam” to distinguish it from the firmer, paler variety. The name stuck, so what you buy labeled “yam” in the U.S. is almost always a sweet potato.
So, the next time you grab a can of “yams” for your holiday casserole, know you’re actually holding a sweet potato. A real yam looks more like a rough, bark-like log with white or purple flesh, and it’s starchy, not sugary.
But don’t worry—you’re in good company. Even famous chefs get this wrong, and honestly, for most recipes, the swap is perfectly fine.
