Few plants are as dramatically beautiful as a wisteria in bloom, its chains of lavender flowers dripping like little waterfalls from the branches. But how frustrating that this delightful early bloomer grows only shoots and no flowers!
This common complaint often can be traced to something as simple as an immature plant or a poor site. Wisterias propagated from seed usually require many years to bloom, so plants should be propagated from grafts, cuttings or layers.
Sometimes, though rarely, winter cold kills a wisteria's flower buds, which is in evidence in the spring. Japanese wisteria withstands the cold better than Chinese wisteria. The Japanese variety also has blossoms that are more fragrant and on longer chains.
Perhaps a wisteria plant isn't blooming because of insufficient light. It needs six or more hours of full sun.
Even with a good plant and a good site, wisteria has a natural tendency to put its energy into rampant shoot growth rather than into blossoms. Heavy pruning, especially in winter, or heavy fertilization makes this problem worse.
Pruning a wisteria in summer will keep the plant tidy and still get it to bloom. Ideally, a wisteria vine is trained to a permanent framework of a trunk and a few permanent arms.
Summer pruning is directed at side shoots that grow off the arms. If an old vine has no defined framework, one winter pruning can create this framework from the existing tangle of stems.
The goal in summer pruning is to make side shoots into short "handles" from which the drooping blossoms hang. One way to do this is to cut the end of each side shoot after it has grown six leaves, then go back in winter and trim them back to a couple of inches.
There are other ways to prune. For example, pinch off the tips of all side shoots a few times during the growing season, or cut them monthly to two or three buds.
If you'd rather not bother with pruning wisteria after it blooms, just ignore it. With age, wisteria takes on a rugged, picturesque look. And eventually, given a good site, it will bloom.