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Is it safe to prune Wisteria this time of year?

Posted: Thu Apr 01, 2010 6:53 pm
by smeep
Hi everyone, I recently moved into a house that has Wisteria planted next to a trellis which is next to a fence. It is completely overgrown to the point that there aren't even any Wisteria leaves showing -- all I see are four or five canes coming out of the ground, heading up the trellis, and then disappearing over the fence into the neighbor's yard. It looks like five pieces of thick rope with no leaves or branching. From that point on it is difficult to determine what's going on; the neighbor has Bougainvillea planted at roughly the same spot on his side, and that has come over the fence and taken over the trellis. The Bougainvillea is so overgrown that I originally thought it was growing from *my* yard. Last weekend I removed a ton of dead wood, which revealed the Wisteria canes. Peering over the fence, it looks like a rats nest of 1" thick vines snaking all over the place. Hard to tell which vine belongs to which plant.

From reading up on Wisteria, it seems that you should prune it in late Summer after the flowers fade and also in Winter. However, I'm trying to get this garden under control now. Do you think it would be ok for the plant if I cut some or all Wisteria canes down to about 2'-3' in height now instead of waiting until Summer? That would allow it to start over and I could train it up the trellis and get some lateral branches, too.

I live in Southern California where the weather is relatively constant, I don't know if that affects the Summer/Winter pruning schedule or not.

Thanks for any advice!

Posted: Thu Apr 01, 2010 7:20 pm
by smeep
Thanks for your reply. I had read that you shouldn't cut back some plants during the growing season because they've used up all their stored energy for growing. Pruning it at that point, they said, leaves the plant weakened. I don't know if that's true or applies to a vine, though, but that's why I posed my question.

I've been really cutting back the Bougainvillea, and have it about 60% pruned back now. Still more to go. I've been cutting all the tiny branches back to where they join a larger branch, and I've been cutting off all the dead wood. I don't really know what I'm doing, but as it has been growing out of control for probably at least six years, you can imagine how many little branches are shooting off in all different directions. My goal is to remove the wily branches and leave it with a few strong support branches growing in the direction I want. I guess we'll see over the next year if this is manageable or not.

But you don't think it will be harmful to the Wisteria to completely chop it off like that? Prune these 15'+ canes all back to two or three feet?

Posted: Thu Apr 01, 2010 7:52 pm
by cynthia_h
It's generally considered risky to prune more than 1/3 of a plant in a given season. It can leave the plant without enough leaves or other resources to support its own growth.

If the plant needs to be cut back severely (and my in-laws had a fig tree in this situation), 1/3 this year and 1/3 next year will definitely take care of it. Because I've somehow, through the requests of friends and others to "look at" their fig trees over the years, gotten familiar with fig branches and their quirks, I didn't need to mark my in-laws' branches as to which ones had been cut back and which ones not.

But the tape used for tying branches to trellises or (heck) even used pantyhose will mark the pruned branches until it's time to deal with the plant again next year.

Cynthia H.
Sunset Zone 17, USDA Zone 9

Posted: Thu Apr 08, 2010 5:33 pm
by smeep
Cynthia, thank you for your reply. That's good to know. I pruned back about 1/3 of the vines, and next year will take care of the rest. I don't own any pantyhose, but I think I'll be able to figure out which vines to prune next year. :-)

Posted: Fri Apr 09, 2010 6:23 pm
by The Helpful Gardener
Wisteria being the rampant beastie it is, I would feel comfortable with another pruning after flowering. This is one of those vines like grapes that seems to thrive on hard cutting, and you will get better flower set for the next year's set-up that way (and not have to wait so long to get it back to good).