Sweet potatoes bloom in my garden at the end of the season (midAtlantic, USA) - day length and stress are triggers. The blossoms are showy but often hidden below the foliage so you have to poke around a bit to find them:
They set fertile seed, although some varieties seem to benefit from/require cross pollination with another. Bees do like the flowers. The offspring are variable in character, as one might expect, but I know folks who are breeding/selecting new varieties. The example above shows buds, flowers and seed capsules on a purple leaved variety grown primarily for its ornamental value (the roots are pretty good too!)- this photo was taken at the very end of a hot, dry August. This variety is self-fertile and I've gotten pretty good germination with seedlings vary from green to purple with a variety of leaf shapes, so there is a lot of genetic diversity in there!