in fertile, free-draining soil after frosts are finished in your area. They are frost-tender, so keep plants sheltered in the early stages. Yams take between 6-10 months to produce tubers, depending on the variety and weather conditions. They are ready to harvest when the tops die back. Leave tubers to dry out for about a week, then store in a dark, cool, airy place, where they will last for several months.