I speak from experience.....we help our next door neighbor cut back his wisteria right after it blooms in the spring to make it bloom the following year. It works every time. We cut it back by as much as 1/3 to 1/2. It RECOVERS quickly. LOL! But it can also be cut back a couple of feet from the tip ends right after it blooms in the spring if you don't want to be so drastic. It blooms heavily every spring and is a beautiful green the rest of the summer.
One year the wisteria kept hitting our neighbor in the face while he was mowing, he got mad and cut it all the way to the ground. The next spring it was so heavy with flowers that you could not see the branches. It was absolutely beautiful! If we had one in our yard, I would cut it to the ground right after it blooms every spring. And like I said above, they recover quickly and are pretty all summer long.
If your lawn fertilizer is washing over into the soil of your wisteria, it will not bloom. Lawn fertilizer will cause pretty green leaves, but no flowers not only on the wisteria but any flower or shrub.
You can do the same with honeysuckles and trumpet vines.
------------
2006 added to the above:
Hello there, if you live where there is little rain fall, you will not have trouble with your wisteria growing out of bounds. But if you live where you have plenty of rain each year, your wisteria will be hard to control. We live in the southwest's semi-desert, our next door neighbor's wisteria gives us no problems at all. It has stayed the same size for over twenty years.
Another thing you can do is plant them in BIG, BIG, BIG containers. Be sure to have something strong that they can climb on such as a metal trellis that is in the ground beside the container. They do get heavy.
If it gets too wild, you can cut wisteria to the ground and it will come back for you the next year.
Information so you will grow a beautiful tree:
(from: http://www.traxfarms.com/info_tips/nursery_tips.htm#wisteria )
"Wisteria
Wisteria is a pretty carefree grower. It can be stubborn with its bloom, but when it does bloom it is spectacular. This plant must have sun, less than full sun retards flowering. All wisteria need well-drained soil that has been loosened at least 2 feet down; this gives the roots room to sprawl. If the soil is poor, add sand for drainage, compost or peat moss to lighten the texture. When planting, position the plant so the graft is above the soil line. Keep the new plants well watered until new growth begins and never let them dry out.
Wisteria is a heavy vine that needs a sturdy trellis or arbor. The trunks can be manually twisted or braided and the rapid growth of the vines makes twisting and training easy. Position the vines in place, stake, and tie with a soft cord.
Wisteria grows quickly and can live for decades. It will survive almost anywhere, but getting it to flower is not easy. Fertilize in late spring with a high phosphate fertilizer around the base of the trunk. Do not use a high nitrogen fertilizer; this promotes new vegetative growth and fewer flowers. Keeping the vine under control helps divert energy to flowering. Also make sure it is in full sun. Root pruning is often recommended to slow growth. With a sharp shovel blade, cut into the soil around the trunk. Stay at least 2 feet away from the trunk to form a circle 4-6 feet across. The vines should also be pruned back by cutting 2 feet or more from the tips. A regular mid-July/August pruning will boost flowering. New vertical growth should be trimmed and suckers at the base of the plant removed.
Wisteria is one of the most trouble-free plants with no significant pests or diseases."
(If your lawn fertilizer is washing over into the soil of your wisteria, it will not bloom. Lawn fertilizer will cause pretty green leaves, but no flowers not only on the wisteria but any flower or shrub.)