Question
QUESTION: My wisteria was taking over my arbor, so over the winter I carefully cut it back about 20-25%. We're into May and I don't have one leaf yet and 3 or 4 flowers bloomed. I'm crushed as it usually blooms twice a year and is so lush and beautiful. Should I not have trimmed it back? Will it ever be like it was?
Sad
Syracuse, New York

ANSWER: Roger, I am so sorry about your wisteria!  Before I can consider your question thoroughly, though, I need to ask you a couple of questions.  Wisteria, as you know, are incredibly tolerant of pruning. At what time of year did you cut it back?  How old is your wisteria? Additionally, can you tell me what sort of winter you had in Syracuse?  (Besides COLD, because that's probably a given!)  Did you have a period of unusually warm weather before more hard freezes?  I'm trying to get a handle on other factors that might be contributing to a lack of foliage/buds.  The only other causes I can think of would be some sort of systemic blight - have you noticed any cracking or discoloration on the trunk or shoots?  I lost a wisteria some years ago to a fungal disease, and I'd like to rule that out.  Sorry to toss questions back at you, but I'm hoping that - together - we can get to the "root" of your problem!  Kind regards.

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QUESTION: I pruned it in January, the winter was milder than normal as far as snow and the summer wasn't really hot. Doesn't seem to be any signs of disease. It's 10 years old

Answer
Well, if we rule out disease (hard to do remotely/on-line) or any insect problem (such as borers) - again, tough to do at a distance - the only other advice I can offer is that perhaps it's a soil problem.  Most people advise against giving Wisteria too much nitrogen-based fertilizer (N is the first number on the three-number fertilizer bag; if that number is larger than the other two, it's a high-nitrogen fertilizer), mainly because foliage is rarely a problem with Wisteria.  Usually, people complain of too much foliage and not enough blooms, in which case they are advised to use a fertilizer higher in phosphorous (the second number on the fertilizer bag).  My advice is to try two things:  (1) give the plant a bit of high-N fertilizer and see if that jump-starts some foliage production, since foliage (as opposed to flowers) is essential to a plant's long-range health. (2) Try a round of root pruning.  This has worked for me in the past with both wisteria and lilac.  Cut off all root suckers at the base of the plant.  Then take a sharp, square-bladed spade and slice 45-degree angled cuts towards the base of the plant all the way around in a circular pattern, approximately 8-10" away from the main trunk.  This root pruning sometimes shocks the plant into action.  Sounds harsh, I know, but it's worked for me.  Keep me posted, ok?