I have two wisteria plants that I've been trying to train up my arbor. This is their third year and they've never really gotten established. The vines are still puny, and they've never reached the top of the arbor (8'). They're planted next to the posts (4x4s).

Any advice on how to make the wisteria grow better this year?

During the spring and summer, they get watered by my lawn sprinklers 3 times a week. I usually give them supplemental deep waterings once or twice a month.

Is there any fertilizer/nutrients I should give them to make them grow and climb this year? Bonus points for making them bloom (which I know is a long shot). Shouldn't they have been established by now?

Thanks!