Are sweet potatoes and yams the same thing? This can be a very confusing subject because the terms are used interchangeably in the US. Here in the States, the term "yam" is commonly used as another name for sweet potatoes. But yams and sweet potatoes are actually two different vegetables.
Differences Between Sweet Potatoes and Yams
Yams belong to the genus Dioscorea which includes several different species. There are white yams, potato yams, yellow yams, Asiatic yams, and Chinese yams. These are different from sweet potatoes, which belong to the genus Ipomoea.
Unless you live in a tropical climate or near a specialty grocery store, you've probably never actually had a true yam. Yams are native to Asia and Africa and have a scaly brown skin. They have a much higher starch content than sweet potatoes and are usually boiled or slow braised as opposed to being baked.
Much like sweet potatoes, yams are heat-loving plants and grow best in temperatures above 75°F. But unlike sweet potatoes which are grown from plants or "slips," yams are propagated from tubers like Irish potatoes. Some yam varieties may also be perennials with the tubers increasing in size each year.
Why Do We Call Them Yams?
If sweet potatoes and yams are so different, why do we use the term "yam" for sweet potatoes here in the US? Some say that southern farmers are to blame. In the early 20th century, all the sweet potatoes in the US were white-fleshed sweet potatoes. As newer, orange-fleshed varieties were introduced, southern farmers used the term "yam" to differentiate the newer orange varieties with the older white varieties. And obviously, it stuck!
Call them what you want, but those little orange pucks you have on the table at Thanksgiving are sweet potatoes. They're sweet and delicious and taste completely different than a true yam. Actual yams are very popular in other countries, but not very popular here in the US.
We do have a variety of sweet potato called "White Yam," but this is also a sweet potato. We don't carry true yam plants or yam tubers. But we do have many amazing sweet potato varieties that you can grow in your backyard garden. Maybe one day we can all get back to calling a sweet potato a sweet potato and a yam a yam!