My lovely sister decided to eat the tuber of an ornamental sweet potato vine (Ipomoea). No she is not three. I was afraid it was poisonous, not so. You may eat it if you like. It doesn't look quite right though, kind of whitish instead of orange. She said it tasted good. I'll take her word for it. Seems like my b-i-l said his websearch showed that it was actually related to regular sweet potatos.