The truth is that some wisteria vines are infertile and never flower. Wisteria does tend to flower best when slightly stressed so do not fertilize but try this: Take a shovel and cut into the root area of the vine damaging half the root system. Sometimes this is a shock enough to get the vine to produce blooms as it thinks it may die without procreating. If you have a sterile plant then nothing you do will can make it flower. If the shovel treatment above does not produce blooms in one year, then throw in the trowel, dig up the worthless wisteria and start over with a plant that you purchase in full bud or bloom. Good luck and be tough - life is too short to put up with disappointing plants. Keep growing, Marianne Binetti