Thanks for writing. This is one of the most common questions we get. Wisteria can be a very fussy plant when it comes to blooming for the first time.
It's not uncommon for wisteria to need 7-10 years to bloom for the first year, especially if it was grown from a seed (versus a cutting). So patience may be only course.
Like many vines, wisteria likes to put on lots of leafy growth. If your soil is too rich (or you fertilize it too much), it will put most of the nutrients into leafy growth vs. flowering. So cutting back on the water and fertilizer may help. Keep in mind, too, that if your wisteria is growing next to a lawn that gets fertilized that the vine may be absorbing some of the lawn's high-nitrogen fertilizer.
While I've heard of lots of gardeners who try root pruning to shock the vine into blooming, I've never seen any real evidence that this works. However, the way you prune the branches can impact how the vine flowers.
In summer, cut off the ends of all new side-shoot branches at the eighth leaf as soon as that leaf unfurls. This type of pruning will encourage new shoots. Cut these new shoots back as soon as only two leaves develop. Then in winter, cut back those side shoots you pruned in summer to a couple of inches from their base.
I hope this helps! Good luck!
---Justin, Senior Garden Editor, BHG.com