News release: Sweet Potatoes

Tim Baker, MU Extension Horticulture Specialist
102 N. Main, Suite 1, Gallatin, MO 64640
660-663-3232, bakert@missouri.edu

Release Date: November 1, 2012

Title: Sweet Potatoes

As we approach Thanksgiving, we are often reminded of the holiday’s origin, with images of Pilgrims and Native Americans celebrating a bountiful harvest. Certain foods are associated with the holiday as well, especially turkey. But vegetables played a role in that celebration too, with several crops that were native to the Americas. Native American crops that quickly come to mind include corn, squash and pumpkins, but that list should also include sweet potatoes.

            The sweet potato is classified in the same family as morning glory, and grows as a vine-type plant. They are tropical plants, and need a fairly long growing season to develop roots that are large enough to eat. Fortunately, they can be eaten at any stage, and don’t have to ripen. So if cold weather cuts the growing season short, you can eat whatever the plant has produced, no matter what the size of the roots.

            Unlike the Irish potato, which produces an edible tuber, sweet potatoes produce a storage root, which we eat. Tubers are modified, underground stems, which differ botanically from roots. Sweet potatoes are also not the same plant as true yams, which are classed in a different family. Sweet potatoes are an excellent source of vitamin A, vitamin C, and potassium.

            I’m not sure if the Pilgrims enjoyed sweet potatoes at that first Thanksgiving dinner or not, but they may have already been familiar with them before they came to America. Columbus found sweet potatoes on his first voyage, and took them back to Europe. They were widely cultivated in Spain, Portugal and Italy during the 16th century.

            Sweet potatoes used to rank higher in importance than they do today. Before World War II, they were second only to Irish potatoes in importance of all vegetables. In 1920, for example, the average person consumed around 31 pounds of sweet potatoes annually. By 1940, consumption was down to around 21 pounds. Today, we’re closer to 5 pounds annually.

            If you want to grow sweet potatoes, keep in mind that they are a tropical plant, and require hot weather to do well. Plants are started from roots, which are grown in hotbeds. The small plants arising from the mother roots are allowed to develop their own root system. Then, they are pulled from the mother roots, and are called "slips," which are transplanted in the field.

            Sweet potatoes do not tolerate frost. In fact, they are subject to chilling injury, where plants are damaged at cold temperatures which are well above the freezing point. They should be harvested before or immediately after the first frost. After the weather cools off, the roots won’t grow much more anyway, so you may want to harvest before frost.

            Sweet potatoes may be stored for some time, but they should be kept relatively warm, compared to other storage crops. The ideal storage temperature is between 55 and 60 degrees. Don’t store them where the temperature will drop below 50 degrees. Cover them with plastic to keep the humidity up, but check them from time to time to make sure it isn’t too moist. Be sure to remove any rotten, decayed roots.