I have a wisteria that has gone untamed for a few years, and I need to know when and how to go about pruning it back to a reasonable size. It grows up the fence to a pergola-like structure, but it’s gone way past that to begin attaching itself to surrounding trees.
Local pruning expert Cass Turnbull of Plant Amnesty has written about pruning wisteria. Here is a link to the article on Plant Amnesty’s website. The relevant passage (about renovating an out-of-control vine) is excerpted below:
RENOVATION. If it gets away from you or you have moved into a home that already has an enormous wisteria tangle, grabbing and strangling everything in sight, show no mercy. Lop, saw and chain saw whatever is necessary to get it back down. I suggest you cut several feet below where you want the regrown vine to be, since you will experience an upsurge of new shoots the following spring. As with all heading cuts, the new growth occurs directly beneath the cut and heads up from there. You will need some room to let it regrow over the next few years. New
growth will be vegetative (not flowering) and rampant for a few years. I wouldn’t be surprised if some major stems die back partially or totally, if you make cuts one inch or over. But I doubt that you will kill the plant. As some stems die back, cut off the dead bits. Others will supply the replacement shoots to be tamed in upcoming years.
Local gardener Ciscoe Morris also has information about maintaining wisteria vines. Excerpt:
“To prevent damage to your house and to encourage flowering, prune the tendrils to about 4 inches from the main structural vines when they grow beyond a foot long. This is a form of spur pruning. It encourages flower buds to form by concentrating all of the energy that would have been used to grow the long tendril into a 4-inch stub. While you are at it, you may as well construct a shed under the wisteria to store your ladder, because within only a few weeks, new tendrils will begin to grow and you’ll be climbing up to do it all again.
The Royal Horticultural Society also has information on pruning and training wisteria in an article entitled Pruning and Training Wisteria.
According to the American Horticultural Society’s Pruning & Training (edited by Christopher Brickell; DK Publishing, 1996), the times to prune are midwinter and again in summer, about 2 months after flowering. With
an established wisteria, the goal of regular pruning is “to control extension growth and to encourage the production of lateral flowering spurs. The current season’s shoots are cut back in two stages to within two or three buds of their base. These will bear the coming season’s flowers. Growth and flower buds are easily distinguished in late winter,
the former being narrow and pointed, the latter plump and blunt.”