Botanically, it’s pretty clear cut.

Sweet potatoes are the root vegetable traditionally eaten at Thanksgiving by millions of Americans while yams are a superficially similar tuber grown in tropical regions of Africa.

But culturally? That’s another story.

Africans brought to America as slaves in Colonial times called the sweet potatoes they encountered here yams, because they looked like the vegetable that was an African staple crop. Hundreds of years later, it’s tough to buck the trend.

The misnomer sometimes causes confusion, said Jeremy Fookes of AV Thomas Produce, a California producer of sweet potatoes.

He’s fielded calls from bewildered shoppers trying to purchase the ingredients listed on a recipe and finding themselves stumped in the produce department looking for yams when all they see are sweet potatoes, or vice versa. In fact, anything listed as a yam in an American grocery store is almost without exception a sweet potato.

At Sacramento Natural Foods Co-op on Tuesday, customers preparing for their holiday feasts packed the produce section, many making a stop at a prominent display of large, red-skinned sweet potatoes popularly known as yams. The co-op sticks to their correct name, which sometimes causes confusion, said produce manager Rick Kilby.

In those cases, produce workers explain the history of sweet potatoes and most of the time people accept it.

“Although we’ll get some customers who are steadfast in their belief that they’re really looking for are yams and don’t believe that what they’re buying are yams,” Kilby said.

Kilby said he’s sure that African tuber would not be a satisfactory substitute for traditional Thanksgiving holiday sweet potato side dishes and pies, and other experts agreed – African yams are starchier, drier and less flavorful than sweet potatoes.

A USDA subcommittee “Can the Yam” convened to bring clarity and conformity to the world of sweet potato marketing, said Fookes, who headed the effort. While it might seem like nothing more than a semantic issue, there is a governmental agency that regulates how foods are labeled to ensure consumers get what they pay for.

The end result was a ruling that allowed use of both sweet potato and yam – as long as the terms are never used deceptively. Traditionally on the West Coast anyway, sweet potatoes with orange flesh are known as yams.

Fookes said there are about five main types of sweet potatoes, with color of the flesh ranging from white to orange to purple, which possibly adds to the confusion. And while they are all members of the same family, they have slightly different attributes that suit them to different dishes.

The orange varieties (traditionally called garnets, although the actual garnet variety isn’t in widespread cultivation, Fookes added) make good pies and sweet dishes, and the white Muraski variety makes an good substitute for regular white potatoes in recipes.

But all carry the health benefit for which they are so strongly recommended by doctors and dieticians, Fookes said, explaining that the same confusion over which sweet potato to use in a recipe comes out in the nutritional context. He added that one type stands out for antioxidant content: the purple varieties. Although they tend to be more bitter than others, he recommended the Stokes purple sweet potato for flavor.

However, you slice, mash, bake or boil them, botanically, a sweet potato will never be a yam. But culturally, the orange sweet potatoes we eat at Thanksgiving might always be one.

After all, ‘candied sweet potato’ just doesn't sound right, does it?

“It doesn’t roll off the tongue the same way, you’re right,” Fookes agreed.