I had never planted sweet potatoes in my life, until... one year I discovered a "store-bought" sweet potato in the back of my cabinet, growing sprouts all over. Since I had an empty raised bed, I just buried it in there and left it all summer to enjoy the spreading greenery in the garden. In the fall when the vines started dying back, I dug up the flower bed and to my surprise, ended up with a laundry basket full of sweet potatoes of all sizes!