Answer: Patience is sometimes the only thing you need to apply to get your wisteria to bloom. It is natural for these vines to take between three and seven years to start blooming. I have read that frequent, proper pruning may help them to begin blooming sooner, or at least more. On the other hand, some people have old vines that have never bloomed. I am told that these are seed grown plants or ?mules?. I have often heard root pruning recommended to force an older vine to bloom. Basically, this means that you use your shovel to cut the roots in a circle (or dotted circle) a foot or two from the vine. I have also heard people recommend fertilizer formulated to encourage blooms, (not heavy on nitrogen). I think the best course of action is to take no action at all. Give our wisterias a chance to become established and they should reward you with fantastic blooms.
Best wishes with your wisterias!
Q&A Library Searching Tips