The Difference Between Sweet Potatoes and Yams is a Lot©
By Arlene Wright-Correll
The other day my mind wandered, like it often does, and I started to think about sweet potatoes and yams. Was there a difference? If so, what was the difference?
My research leads me to discover that the true yam is the tuber of a tropical vine (Dioscorea batatas) and is not even distantly related to the sweet potato. I learned that 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 and that surprised me.
I went on to discover that generally sweeter than the sweet potato, this tuber, the Yam, can grow over seven feet in length and that 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 higher moisture content. Often Yams are also marketed by their Spanish names, boniato and ñame.
For the most part, it does not grow well in the United States, even with care - most of the US is too cold. Yams are a subtropical/tropical vine, growing best in zone 9 or higher. Some can grow in zone 8 with care. In parts of zone 7, it can be grown as an annual, ornamental vine, but it won't produce many tubers, if any. Since Yams are vines, and need trellises for support of their vine canopies. They need more space than what is available in a tire stack or a 30 gallon bag, so planting them in the ground is best - 3 feet apart and 3 - 4 inches deep. Setts, seeds, or cuttings can be planted - yams, under the right conditions, are very fertile. They require sandy clay loam augmented with loose compost. It takes 10 months for the tubers to form. The ground must stay warm the entire time - 77*F or warmer and night time temps need to remain above 77*F for 9 or 10 months, so that lets Kentucky out at least I think so.
Sweet potatoes, which are 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. Now I know the difference, but will I remember not to confuse the names?
The world is full of mysteries!