non blooming wisteria

the plants are 7-8 years old, lots of foliage, leafy and very green, but no blooms, on a large arch, in fact they almost cover the whole thing.
I have tried root pruning, triming back the stems,with holding fertilizer. WHAT AM I DOING WRONG!!!!!!!!!

oodles of sunshine.Annabelle! The secret is...some Wisterias are species and others are grafts..whichis yours? So. the pruning back of the strongest shoots to 2 buds is the way to go..lay off any Nitrogen fert. and go for Potassium...this is the method I used and it worked..so the same time you take away from the vine, give something back to him....I hope this helps! Elaine