Don't ask me why. I've tried to figure it out to no avail. My wisteria thinks it's great to bloom in late August or early September after a full growing season.
No matter how many times it's done it in the past, I'm still surprised when I come upon a bloom. The heady fragrance is fantastic... but somewhere deep in my head I know that scent belongs to the springtime.
There were years after I first put it in that it didn't bloom at all. I was dismayed and tried carefully not to over-prune it in the fall or winter so it would bloom in the spring.
It didn't work.
The first time it finally bloomed was in the autumn with all it's gorgeous green leaves still intact. I should have known that was a portent of years to come.
The past couple of years, the silly thing has decided to bloom twice a year. Yes... TWICE. And it isn't a prolific bloomer for either the spring or late summer/early fall blooms. I get a few clusters and that's it.
I always had visions of a wisteria like my mother's. Hers grew huge on a latticed pergola with the massive bluish-purple clusters hanging down through the lattice to brush my head as I walked under them causing the petals to flutter down at my feet.
Yes... that was my vision. But that isn't what I got.
Instead, I got a weird wisteria that does things completely out of sync from what wisteria is supposed to do.
It shouldn't surprise me though. I do pretty much the same thing. *wink*