Although the names are commonly used interchangeably, yams and sweet potatoes are actually two different plants. Yams are monocots, having only one seed leaf, such as grasses, corn and lilies. Sweet potatoes are dicot plants, with two seed leaves, such as beans and roses. The sweet potato is a “storage root” of a vine, a member of the morning glory family, while the yam is a “tuber” or underground swollen stem.

Yams are grown from tuber pieces and sweet potatoes planted as transplants from vine cuttings or as small slips from the potato eyes.

How to tell them apart? A sweet potato will have a smooth appearance with a thin skin, and are short with blocky tapered ends. Flesh of a sweet potato is bright orange, moister and sweeter tasting than yams.

Yams are a tropical plant, and take about a year of frost free weather to develop. They are typically imported from the Caribbean, and have a rough appearance with a scaly skin and are longer and more cylindrical than sweet potatoes. The flesh of a yam is rather dry, and usually a pinkish-yellow in color.

Sweet potatoes take about 100 to 150 days to reach maturity. Iowa State University recommended sweet potato varieties for growing in Iowa include ‘Georgia Jet’, ‘Centennial’ and ‘Beauregard’.

Did you know? Both yams and sweet potatoes are a great source of fiber. The sweet potato is high in Vitamin A content while the yam is rather low in Vitamin A. For the most food value, choose sweet potatoes of a deep orange color.

Horticulture Questions? Contact McCormick at yvonne@iastate.edu for information or advice.