This may shock you, but true Yams are not native to the United States. Uh huh, that is right. Yams are not even distantly related to sweet potatoes. Here is a picture of a true Yam.

That gnarled, shrivelled looking thing does NOT look like any kind of sweet potato that Americans are familiar with.  Yam is the common name for some species in the genus Dioscorea (family Dioscoreaceae). These are perennial herbaceous vines. It is commonly used in African & Asian cooking. 95% of the world's true Yams are grown in Africa.

There is a lot of confusion on this issue. Many grocer's don't even know the difference, nor do they have them labeled as such in the store. In the US, the "yams" that we refer to are actually a cultivar of sweet potato. There are even canned "yams". But those are really sweet potatoes.

In the United States, firm varieties of sweet potatoes were produced before soft varieties. When soft varieties were first grown commercially, there was a need to differentiate between the two. African slaves had already been calling the 'soft' sweet potatoes 'yams' because they resembled the yams in Africa. Thus, 'soft' sweet potatoes were referred to as 'yams' to distinguish them from the 'firm' varieties. The 'soft' sweet potato is the bright orange fleshed potato that most refer to as sweet potatoes.

Today the U.S. Department of Agriculture requires labels with the term 'yam' to be accompanied by the term 'sweet potato.' Unless you specifically search for yams, which are usually found in an international market, you are probably eating sweet potatoes.

To differentiate between the two that we are familiar with, yams in our grocers are bright orange fleshed and very moist. They can be quite sweet and very moist and they look like this: This is what you will want to use in most recipes that call for "sweet potatoes", such as Sweet Potato Pie & Candied Yams.

The lighter fleshed variety that you will see often labeled in grocery stores as a "sweet potato" have a texture similar to an Idaho potato. They are starchier, drier, and not nearly as sweet, even though they do have a sweeter flavor than an Idaho spud. These tend to crisp up better than the more orange variety in the oven when you are making oven baked fries.

This is what you will see labeled as a "sweet potato".

To add to the confusion, there are other varieties that are red fleshed & purple fleshed sweet potatoes as well! So when you are trying to decide which one to use in a recipe, you have to use your best judgement. Just know that many grocers will have them labeled erroneously as "yams".