November 13, 2003

 

Is it a Sweetpotato or a Yam?

By Ron Smith, Horticulturist
NDSU Extension Service

Every year we are confronted with the sweetpotato or yam question for Thanksgiving meals. The confusion started several decades ago when orange-fleshed sweet potatoes were introduced in the southern U.S., producers and shippers wanted to distinguish them from the more traditional white-fleshed types.

The African word nyami, referring to the starchy, edible root of the Dioscorea genus of plants, was adopted in its English form, yam. Yams in the United States are actually sweetpotatoes with relatively moist texture and orange flesh. Although the terms are used interchangeably, the U.S. Department of Agriculture requires that the label "yam" always be accompanied by "sweetpotato."

Sweetpotato (Ipomoea batatas) is written as one word because the crop is distinctly different from potato (Solanum tuberosum) and yam (Dioscorea spp.) which are also grown and marketed in America. While sweetpotatoes are commercially grown in the southern United States, some varieties have been developed that can grow in the southern fringes of the northern states, and require a minimum of 130 frost-free days to be decently productive for backyard gardeners.

Yam is a tropical crop important in north China, Japan, and West Africa, and only in the most southern regions of Florida. In contrast to sweetpotatoes, yams are dry, starchy, and light-fleshed. They are also much larger than a sweetpotato, growing to between 3 to 8 pounds each. A poly-film bag filled with sweetpotatoes would weigh that much.

Nutritionally, the sweetpotato is the unquestionable heavyweight, being one of the leading vegetable sources of vitamin A. Sweetpotatoes are also a good source of vitamin C, fiber and protein.

The yam is a nutritional wasteland by comparison; no vitamin A or any other vitamins of worthy mention. The only place the yam wins is in the calorie department -- something few of us need. Besides, we'll get plenty of those over the Thanksgiving holiday anyway.

###

Source: Ron Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Tom Jirik, (701) 231-9629, tjirik@ndsuext.nodak.edu