n the United States, sweet potato (Ipomoea batatas), especially those with orange flesh, are often referred to as "yams." In the United States, firm varieties of sweet potatoes were produced before soft varieties. When soft varieties were first grown commercially, there was a need to differentiate between the two. African slaves had already been calling the soft sweet potatoes "yams" because they resembled the yams in Africa. Thus, soft sweet potatoes were referred to as yams to distinguish them from the firm varieties. Sweet potatoes labeled as "yams" are widely available in markets that serve Asian or Caribbean communities.
Today the U.S. Department of Agriculture requires sweet potatoes labeled with the term "yam" to be accompanied by the term "sweet potato."
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