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| Photo Credit: Megan Bame |
| Though most people think of sweet potatoes as only being orange, there are also some white varieties, like the one seen here. |
Yams are not sweet potatoes, but sweet potatoes are sometimes “yams.”
Confused yet? Botanically speaking, sweet potatoes are completely different from yams, but if you recall, horticulture allows for different common names – and that’s what often gets us in trouble. The confusion between sweet potatoes and yams apparently arose when producers in the US were looking for a way to distinguish the Southern-grown, moist-fleshed sweet potatoes (which were generally orange) from the Northern-grown, dry-fleshed sweet potatoes (which were traditionally white). The English word “yam” came from the African word “nyami,” which referred to the starchy, edible root of the Dioscorea species (the true yam) – and that’s generally yellow- or white-fleshed. But oddly enough, somehow the word “yam” became associated with the orange sweet potato. The US Department of Agriculture allows sweet potatoes to be sold as “yams,” recognizing that consumers use the two terms interchangeably; but the “yam” label must also include the words “sweet potato” to ensure truth in labeling. (Follow that?) Let’s take a closer look at the differences between these two garden veggies. For starters, they come from different plant families. The sweet potato, Ipomoea batatas, is a cousin of the morning glory in the Convolvulaceae family. The yam, Dioscorea spp., belongs to the Dioscoreaceae family. In the sweet potato, the storage organ we eat is the root, as opposed to the edible tuber that’s produced by the yam. A tuber is actually a swollen, underground stem. (The Irish potato is also a tuber.) A yam plant yields only 1-5 tubers per plant, while the typical sweet potato yield can be in the range of 4-10 per plant (in different sizes).
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