Posted: 21/08/2015 at 17:11
First of all, a couple of questions:- has the plant ever flowered? Apparently it takes quite a few years before they get to that stage, so it's advisable to buy one when it is in flower, so that you know it is mature enough to flower in the following year. Secondly, where is it planted? I ask this because sometimes - when wisterias are planted close to, say, the wall of a house - they suffer from poor soil conditions and lack of water.
To explain a bit further - when I moved to this house years ago there were two apparently well-established wisterias on the front wall. They'd been planted in holes which had been dug out of a concrete path, so got little rainwater, and I guess the soil was very poor indeed. I was surprised that there were no flowers the first year I lived here, despite the fact that the plants themselves had obviously been in situ for a very long time. I read some things about why this might be, and discovered that it was recommended to keep them very well-watered even during the autumn and winter months. Before the concrete path was removed - a couple of years later - I poured literally two buckets-full of water down each "hole" every week or so, and the following year was rewarded with loads of flowers, having done the recommended pruning in late February.
The path is now long gone - there's open ground now in front of the house, with a sort of shrub bed, and the wisterias are now well-known locally as being the most amazing ones people have ever seen! The racemes are often as much as 18" long and look like a purple waterfall down the front of the house.
I think that if any of the above applies to your plant, you could try what I did and see what happens next year. Good luck!