Apparently these take a minimum of 4 months to produce tubers. I planted the rooted cuttings in mid June, after the soil had been well heated up under black plastic. They are trailing all over the ground and slightly resemble ivy. Today whilst watering I noticed a wonderful pink tuber just poking out from the surface of the soil it was about 2 inches thick and 4 inches long - my first sweet potato! Hooray! 