A SWEET POTATO, BY ANY OTHER NAME, IS NOT A YAM
There are many varieties of sweet potato, which are part of the morning glory family. Sweet potato skins range from white to orange-red, and their flesh can be creamy white, yellow, orange or orange-red. In the United States, they are grouped into two categories: firm sweet potatoes have white skin and pale flesh, and soft sweet potatoes have copper skin and orange flesh. The former, when cooked, remain firm and a little waxy. The latter become creamy, fluffy and moist.
So what’s a yam? The word is an anglicization of the African word nyami, which refers to tubers related to lilies and grasses that are native to tropical areas in Asia and, mainly, Africa. These also come in many varieties, with black bark-like skin and white, red or purple flesh. Almost 95% of yams are grown in Africa, where specimens weighing as much as 130 pounds have been recorded. While yams are starchier and drier than sweet potatoes, and though the plants are not botanically related, they are similar in appearance.
In colonial America, when confronted with a sweet potato, it is unsurprising that African slaves called them yams. What is surprising is that American growers perpetuated the labeling error as a marketing device. White, or firm, sweet potatoes were already on the market and well established when orange, or soft, sweet potatoes were introduced. Searching for a means to distinguish the new from the old, soft sweet potatoes were labeled yams. Today, the United States Department of Agriculture continues this fiction, with the proviso that the erroneous label yam be accompanied by the correct term sweet potato. Real yams rarely reach the American market. Your best shot would probably be a Caribbean or international grocery.
