Link to evergreen wisteria (Callerya reticulata syn. Millettia reticulata). On the side note, there are two other types commonly are grown for ornament in the US, the Japanese & Chinese species. http://gardeningsolutions.ifas.ufl.edu/plants/ornamentals/evergreen-wisteria.html

I’m wondering if this is a type of wisteria with an out of season bloom or it’s a late summer/fall blooming evergreen wisteria (Callerya reticulatat syn. Millettia reticulata). Can you give us more photos of the vine i.e. more flowers, closeup of stem, main trunk, seed pods? For now check out these links for a native wisteria species Wisteria macrostachya (Kentucky wisteria), a spring bloomer. Again, I’m only speculating. Best wishes! http://www.cirrusimage.com/tree_wisteria.htm