Tame Your Wisteria
I can’t think of a vine that offers a better combination of beauty and fragrance than wisteria. The pendant chains of blue, purple, pink, or white blossoms transfix all observers, and their scent is so sweet you can smell them from 100 feet away. But be careful if you plant one. You could be planting a monster.
The two most popular species, Japanese wisteria (Wisteria japonica) and Chinese wisteria (Wisteria sinensis), demand the most caution. They use twining stems to climb at an astonishing rate. They never stop growing, so there’s no such thing as a mature height. If you planted one at the base of the General Sherman giant sequoia in California, it would probably reach the top in 10 years. Of course, by that time you’d have been executed, and rightly so.
Asian wisterias spread by other means than climbing. Their roots produce suckers far from the original plant. They also drop seed. As a result of this, entire hillsides near my home in Alabama turn bluish-purple in spring. What’s the harm? Well, the vines can shade out and strangle native vegetation. Where 100 different plants were, now you have just one.
Never plant these non-native wisterias where their stems can reach out and grab a tree or shrub. When I discover non-menacing examples, they’ve often been trained into small, umbrella-shaped trees. It’s pretty easy to do. First, pick a sunny spot that’s at least 20 feet away from any tree, shrub, cow, or texting kid. Plant your vine there and place a sturdy 4 to 5-foot stake next to it. Tie the main stems to the stake at several spots, but don’t let them twine around it, because you’ll eventually want to remove the stake after the trunk gets thick enough to support the top. When the stems reach the top of the stake, pinch out the tips to encourage side branching.
Remove side branches from the lowest three feet of trunk (as well as root suckers), but let the top ones grow and spread in all directions. They’ll do this quickly. Throughout the growing season, the vine will send out long whip-like tendrils used to grab onto things. Let these grow several feet long and then pinch out the tips. They’ll leaf out and become branches that no longer twine. (If all of this seems too much work, you can buy wisteria “standards” that have been trained into a single upright trunk from the garden center.)
After a summer of growth, your tree will look rather unkempt. Give it a haircut in late fall or winter, cutting back each side branch growing from the main stems to 6 to 8 buds. Not only does this tidy up the plant, it produces heavier flowering the next spring.
In the following years, work on letting the main branches get a little longer each year until you achieve a roughly symmetrical umbrella shape. Continue cutting back side shoots to 6 to 8 buds each winter. Remove any seed pods and throw them out with the trash. Mowing under the vine will take care of suckers.
I would be remiss if I ended this without mentioning our native wisterias. They’re much better behaved and unlikely to bring down the house. Look for ‘Amethyst Falls’ American wisteria (Wisteria frutescens ‘Amethyst Falls’ and ‘Blue Moon’ Kentucky wisteria (Wisteria macrostachys ‘Blue Moon’). Their fragrance doesn’t match that of their Asian counterparts, but you won’t lose sleep at night wondering if they’ll be in bed with you the next morning.