If you're putting them in fertile, moist ground now, you should have some very nice size potatoes by the time frost hits. You can eat them, or store them to grow again next year. After being dug-up, sweet potatoes need to be cured. I won't try to paraphrase the experts on that:
http://www.ncsweetpotatoes.com...
Many people report disappointment from harvested sweet potatoes because they skip the curing step. What kind did you get? 'Blackie' and 'Margarita' are delicious, IMVHO. I couldn't tell a difference between those & the kind with normal, medium green leaves, but did like them better just from being jaded about them being "free from the yard."
If you want more plants, just cut pieces of the foliage off & stick in water for 2-3 days until they start sprouting roots. Potatoes from plants started later will be smaller, from having less time to grow. As long as the drainage is good, any potatoes you miss will probably keep growing next year. Definitely hardy here.
