What's the difference between purple sweet potato and purple yam? (potatoes, cooking)

[Audioque]

I've been looking for the Okinawan purple sweet potato for a while but the only thing I came across is purple yam at my local Asian market. I'm wondering if they're really the same thing but was mislabel which is often the case in Asian market. If they're different but their nutritional values are the same, that's good enough for me too.

[Curmudgeon]

Originally Posted by Audioque

I've been looking for the Okinawan purple sweet potato for a while but the only thing I came across is purple yam at my local Asian market. I'm wondering if they're really the same thing but was mislabel which is often the case in Asian market. If they're different but their nutritional values are the same, that's good enough for me too.

While similar, one's a sweet potato and one's a yam which are not related botanically. What are sold as yams are often sweet potatoes, and there are several varieties and colors. True yams are often only found in Asian markets and are starchier, drier and generally sweeter than sweet potatoes.

[OpenD]

It's almost certainly mislabeling. Americans have long mistakenly called sweet potatoes yams, but most have never even seen a real yam. Yams are starchy, not sweet, and are used in Carribbean and Puerto Rican and African cooking.

On the Big Island of Hawai'i purple sweet potatoes grow very well, and are a common item at farmers markets.

What they're selling at the Asian store might even be from Hawai'i, where they are called Okinawan sweet potatoes. But "yams" is easier to write on a sign.

Here are more details on why firm sweet potatoes are called sweet potatoes in the US while soft sweet potatoes are called yams. It comes up every Thanksgiving...

http://www.city-data.com/forum/27131426-post2.html