Expert: C.L. Fornari - 4/1/2010

Question
I HAVE A HEALTHY WISTERIA ON A TRELLIS @ MY GARAGE BUT IN THE TEN YEARS IT HAS BEEN THERE IT HAS NEVER HAD ANY BLOOMS. CAN YOU TELL ME WHY AND IF THERE IS ANY THING I CAN DO TO HELP THE SITUATION.
Midland, NC

Answer
Johnny,
Wisteria are famous for not blooming for the first 12 to 16 years of their life - the best way to encourage it to bloom is to treat it poorly: NO fertilizer (this will just make it grow more leaves - if you've been fertilizing, stop at once and give it no more.) no watering, and no organic matter such as manure.  Prune the plant hard, but cutting off all the long green whips that it forms. Flowers on Wisteria are formed on what are called "bloom spurs" - these are twigs that are between three and six inches long, with buds on them. So if you see anything that looks like that, don't cut those off. All long green growth can be cut back repeatedly through the summer, however. Some people also root prune the plant by sticking a shovel about 18 inches from the trunk and cutting downwards - do this in two or three places, but not around the entire trunk.  Basically, this stresses the plant and helps to encourage it to bloom.

Good luck with it!
C.L.