Both the orange-fleshed and yellow-fleshed tubers are varieties of sweet potatoes, of the genus Ipomoea (morning glory) family, mostly of temperate climes. The orange-colored are sometimes called yams but are not related to the 'true yam' (Dioscorea) of tropical Africa and other tropical areas.
See pictures here: yam and sweet potato

I was wrong in my posts above- I thought the orange-fleshed ones were the Dioscorea type or true yam. I should have checked before posting my 'gems of knowledge'.
Checking other websites, including that of Ohio State University, they agree with the material stated in the linked website.


The Dioscorea yam is not grown in the USA. All sweet potatoes here are Asian varieties of Ipomoea which have become very widespread in planting. Selection of varieties and selective breeding has led to several varieties in grocers bins.

The Dioscorea (true yam) needs a tropical to subtropical climate and is not suited to the United States. It is widely grown in tropical parts of Africa. Any post that states that the yam in North America is an import from Africa is wrong; some are grown in the West Indies but not in the USA. I have made this mistake in some of the posts above.