Wisteria

Is it in apot? I ask as I have had the same problem with bonsai wisterias, and don't know if it is the restriction in a small pot, or they don' tlike the soil mixture, or even if it's because they are old plants. Wisterias I have in large pots are prolific flowerers. The roots grow very quickly - I repot the bonsais every year and prune the roots by a third. Do the leaves and everything look healthy?

What pruning did you do last year?

very little - just trimmed back

That could be the problem - you need to be making flowering spurs. Have a look at:

http://www.rhs.org.uk/advice/profiles0605/wisteria.asp

It covers pruning in detail.