We're trying to overwinter some of last spring's sweet potato vines. Mostly it's worked. There have been a few casualties. It's kind of a long story. In any case, they flower off and on, throughout the winter. And the summer. And the other seasons. 'Blackie' seems to do this more than the other variety we have, a chartreuse kind called 'Marguerite.' 'Blackie' also does a weird thing that kind of looks like a disease but I think is just edema or something:
It only seems to happen when the soil is really, really wet. Doesn't appear to be hurting the plant especially, though. We never got a definite diagnosis, but the timing looked more or less like edema or guttation or something along those lines. (I don't suppose anybody could confirm this for me?) If 'Marguerite' does this, it's much harder to see: I don't think I've ever spotted it on any other variety of sweet potato.
Although I knew that sweet potatoes and morning glories were both in the same genus (Ipomoea), it hadn't really struck me how much the flowers resemble one another until I started writing this post. This is kind of cool. I like when the real botanists and I agree on something.