Yam or sweet potato, many people use these terms interchangeably both in conversation and in cooking, but they are really two different vegetables.
Yams are closely related to lilies and grasses. Native to Africa and Asia, yams vary in size from that of a small potato to a record 130 pounds (as of 1999). There are over 600 varieties of yams and 95% of these crops are grown in Africa. Compared to sweet potatoes, yams are starchier and drier.
The true yam is the tuber of a tropical vine (Dioscorea batatas) and is not even distantly related to the sweet potato.
Slowly becoming more common in US markets, the yam is a popular vegetable in Latin American and Caribbean markets, with over 150 varieties available worldwide.
Generally sweeter than the sweet potato, this tuber can grow over seven feet in length.
The word yam comes from African words njam, nyami, or djambi, meaning "to eat," and was first recorded in America in 1676.
The yam tuber has a brown or black skin which resembles the bark of a tree and off-white, purple or red flesh, depending on the variety. They are at home growing in tropical climates, primarily in South America, Africa, and the Caribbean.
Yams contain more natural sugar than sweet potatoes and have a higher moisture content.
The many varieties of sweet potatoes (Ipomoea batatas) are members of the morning glory family, Convolvulacea. The skin color can range from white to yellow, red, purple or brown. The flesh also ranges in color from white to yellow, orange, or orange-red. Sweet potato varieties are classified as either ‘firm’ or ‘soft’. When cooked, those in the ‘firm’ category remain firm, while ‘soft’ varieties become soft and moist. It is the ‘soft’ varieties that are often labeled as yams in the United States.
Popular in the American South, these yellow or orange tubers are elongated with ends that taper to a point and are of two dominant types. The paler-skinned sweet potato has a thin, light yellow skin with pale yellow flesh which is not sweet and has a dry, crumbly texture similar to a white baking potato.
The darker-skinned variety (which is most often called "yam" in error) has a thicker, dark orange to reddish skin with a vivid orange, sweet flesh and a moist texture.
Why the confusion?
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.
Today the U.S. Department of Agriculture requires labels with the term ‘yam’ to be accompanied by the term ‘sweet potato.’ Unless you specifically search for yams, which are usually found in an international market, you are probably eating sweet potatoes!
Try some of our favorite Sweet Potato recipes:
Roasted Sweet Potatoes with Apples : lots of great flavor
Sweet Potato Casserole : always a holiday treat
Sweet Potato Stew with Chicken (or turkey): delicious for leftover chicken or turkey
Sweet Potato Pudding : especially light and yummy
Sweet Potato Bisque with Peanut Butter : a favorite in our house and freezes well
Turkey Hash with Sweet Potato and Apples : a great light dinner or even as a breakfast.
Look for more sweet potato recipes in the different recipe categories.