PlantLife Online

Answer

I recommend heading down to your local nursery and picking up some starter plants since sweet potatoes are rarely gown from seed and are more commonly grown from vegetative cuttings from a parent plant. Sweet potatoes starts should be transplanted only after the soil has warmed up sufficiently in the spring around 10 days after the frost-free date in your area. Plant 18-24 inches apart. They should be planted in moderately fertile well-drained soil in full-sun. Avoid planting in overly manure rich soils as this may increase the risk of disease. Plants will begin to yield in as soon as 4-5 weeks for larger yield harvest in 120-150 days but before first frost. The skin of the sweet potato is quite delicate so use care when harvesting.

Sweet Potato: http://plantlifeonline.net/plants/vegetables/sweet-potato