I picked up this wisteria on a sale table at a large hardware store at the end of last year. It was looking a bit worse for wear and was barely alive, however, it has come good and is looking a picture at the moment. Though it was named as Wisteria brachybotry 'Okayama' it does not match the description of a dark mauve or mallow coloured flower. Wrong tag in pot quite possibly? There are three different species of Wisteria in general cultivation:W. sinensis (Chinese wisteria) W. floribunda (Japanese wisteria) and this one, though even it is sometimes confused with the American native species W. macrostachya and W. frutescens which are most often found in Missouri, Tennessee and Texas.
In his book Wisterias: A Comprehensive Guide (Florelegium Books), Peter Valder says it is the last species to flower and that it flowers more reliably in its younger years without demanding a regular pruning regime for best flowers. I have planted it in a decorative pot and am hoping for some more 'spot flowering' in the summer months. I came across the photo below of a specimen trained as a shrub with low clipped box as ground cover around it. It looks very elegant. It is in The Education of a Gardener by Russell Page.