Wisteria can really become a monster if you don't keep it pruned fishin and if it's near your house it can rip the house gutters, roof, etc. right off (this is what the garden guy on the radio always jokes about).
He prunes his several times each year and has it growing over his patio arbor.
Ciscoe's To-do List: Unreined wisteria can raise the roof
By CISCOE MORRIS
SPECIAL TO THE SEATTLE POST-INTELLIGENCER
Prune to make your wisteria flower (and save your roof).
There should be an ancient proverb warning that only a dim-dim would plant wisteria within a block of one's house unless you love to work hard. The tendrils can grow 25 feet in one season, and they have an affinity for snaking under and ripping off roof shingles and rain gutters. 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.
Ciscoe Morris, a King County Master Gardener, regularly gives gardening advice on radio and television. His Web site is www.ciscoe.com.