Sweet 'Taters v Yams: What's the Story Morning Glory?

So this is the time of year when traditional holiday food items make their way to the collective front of the national culinary lobe. And - if you are like most people - when the category of sweet potatoes finds its way into conversation for any length of time, there follows a general sense of confusion about what is a yam, what is a sweet potato, whether they are related, and where to get them in the event that you prefer one over the other...

It turns out that - in the United States - actual yams are not that common. Instead, what you ARE likely to see in the produce section of your local grocery store are two varieties of sweet potato - a white or pale yellow variety labeled correctly as sweet potatoes and a second orange, sweeter variety confusingly labeled as yams for obscure historical reasons.

Sweet potatoes, as it happens, are a variety of Morning Glory. Actual yams are the bulb or tuber of a vine that grows natively in more tropical climates such as South America and Africa, and can grow to be quite large (several feet in length and over 100 pounds).

Here's a more scholarly breakdown of the differences, in case you are interested:

http://www.ces.ncsu.edu/depts/hort/hil/hil-23-a.html