Wild sweet-potatoes are closely related to supermarket sweet potatoes. The tuber can be up to 30 inches long, 5 inches thick and weigh about 20 pounds. They're said to be tasty, but bitter if too big. They were a staple of the American Indian diet. The root also has been used medically as an infusion and may have laxative effects, or as a poultice used for rheumatism.