Yams vs Sweet Potatoes – What’s the Difference?
When you gather around the table for your Thanksgiving meal, there's a good chance there will be some form of what someone calls, "yams" there for your eating pleasure. But are you really just eating sweet potatoes?
According to the North Carolina Sweet Potatoes website, there is a difference, and what are often referred to here in the states as yams are actually sweet potatoes.
A true yam is a starchy edible root of the Dioscorea genus, and is generally imported to America from the Caribbean. It is rough and scaly and very low in beta carotene.
Depending on the variety, sweet potato flesh can vary from white to orange and even purple. The orange-fleshed variety was introduced to the United States several decades ago. In order to distinguish it from the white variety everyone was accustomed to, producers and shippers chose the English form of the African word “nyami” and labeled them “yams.”
My guess is all these years your Grandma was slaving away making what she thought were yams, were actually just sweet potatoes. Whether or not you want to tell her that is completely up to you. My advice — keep the peace and let Grammy believe what she wants to believe. She's earned it.
[Source: North Carolina Sweet Potatoes]