This has annoyed me for years. Really, it has! When I saw recently in a Top (hint hint) US supermarket that they had yams and sweet potatoes – but that they were both marked as the other – I just about had a bird.
[Edit March 2011: I’m getting tons of Google traffic for this post, as well as a lot of people showing up without a referring website. I’m extremely interested in knowing where you came from – would you mind leaving me a comment to let me know? Thanks! –Jenn]
The time has come, folks, to set this record straight. Listen up!
The yam is a tuber and a member of the lily family, while the sweet potato is a member of the morning glory family (of all things). Yes, they have scientific names, which Google will happily provide for you if you care enough to search for it.
Sweet Potatoes originated in Central and South America, and come in a variety of skin colours ranging from very light to red, to even purple. The flesh too, can range from white to orange, with the darker colours being sweeter. They are an excellent and yummy source of beta carotene. I adore Sweet Potatoes.
Yams, which originated in Africa and are not commercially grown in the US or Canada, have dark, rough, often shaggy skin, where sweet potatoes have thin skin, and the flesh is generally very light coloured and starchy. Yam tubers can grow several feet in length, whereas sweet potatoes generally stay in the range of a true potato in size, although more elongated in shape.
Nigeria is the largest producer and exporter of Yams (and internet fraud, but I don’t think it’s related).
So why, then, do so many Americans think that sweet potatoes are actually yams?
Interestingly enough, it comes from the dark days of slavery in the United States. African natives who were captured and brought to the states to become slaves thought the sweet potatoes were so like the tubers found in their homeland that they called them nyami (which apparently just means “to eat”), and as these things are wont to do, the word was eventually shortened to “yam”. I don’t present this as absolute fact, mind you – but I have read it so many times that I believe it’s surely close to the truth, if not the spot-on truth.
There is more to this twisted tuber temerity though!
Can you believe the USDA, in their infinite wisdom, actually insists that the label “yam” always be accompanied with the words “sweet potato” when referring to a sweet potato? Have you ever heard of anything so absurd? Surely, in this day and age, this authority on what you put in your mouth would have gotten word that they’ve been wrong all this time and changed their tune. Of course, that would require admitting that they were wrong, and we all know that ain’t gonna happen.
No wonder people are confused. Well, except me. And you – because now you know the truth! Go forth and spread the truth of the sweet potato!