Is your wisteria getting a little aggressive? Here’s how to make it do what you want

A friend recently invited me to visit his yard to offer suggestions for managing some overgrown shrubs. We talked about azaleas, wax myrtles and ligustrum, how and when to prune, fertilize, among other things. I noticed a 6-foot by 6-foot wisteria growing next to a lamppost and thought, “Hmm, nice plant — not the best location.”

My friend mentioned that he didn’t get many blossoms on the wisteria, and I suggested that it be moved to the sunny side yard in the fall and planted to grow on a pergola. I told him to consider planting a smaller, more manageable vine next to the lamppost, perhaps a variety of clematis or mandevilla.

Wisterias are famous for the hanging clusters of blossoms they produce in the spring. Training wisteria on a solid framework and knowing when and how to prune it is the way to get a breathtaking display. Now is the time to perform some vigorous pruning on this plant regardless of where it is located. Cut back the side shoots and lateral vines to about six inches from the main stem, allowing about six buds to remain on each. You may be cutting away a lot of greenery, but it is necessary. Wisteria are very aggressive growers, and the plant will soon resume its rampant ways.

When the wisteria has lost its leaves in winter, you can distinguish leaf and branch buds from flower buds. The flower buds are plump and have a blunt end, whereas the other buds are much narrower and taper to a point. Winter is the time to perform the second pruning of the year. Cut all the branches to three to five flower buds so that energy is directed to flower production rather than vegetative growth. Wisteria do not need to be fertilized; doing so will just encourage more vines and leaves, at the expense of flowers.

Here are some caveats for those of you thinking of planting wisteria. The fruit is a flattened, velvety bean pod about 2 to 4 inches long containing poisonous seeds. In late summer the bean pod cracks open and releases the seeds. A fully bloomed wisteria is a bee magnet. Use caution, especially if someone in your home (or a visitor) has bee allergies.

The root systems can spread very wide and create problems with underground plumbing. Consider surrounding the root system with a 2-foot-high, 3-foot-diameter circle of thick, galvanized metal when doing the initial planting.

Other plants which benefit from being trimmed in July are African iris, agapanthus, pentas, and coleus.

Cut just under the green seedpod of African iris with scissors to remove the pods as they appear, in order to keep the iris from self-seeding. Do not cut back the flower stalk, since it is perennial and will produce more blooms. Cut brown or yellowing leaves and stalks back to the base of the plant with pruning shears. Remove them one at a time; the leaves are tough and difficult to cut through.

After they bloom, cut the stalks of agapanthus to the base of the plant. You want this plant to direct its energy toward producing strong root growth for next year, not to waste it on seed production.

Pinch off dead blossoms of pentas during the blooming season, to encourage further flower production, until it is too cold for any more blooms to appear.

Coleus require regular pinching back to maintain full form and vigor.

Pinch off the growing tips selectively in areas of the plant where growth appears spindly or leggy. Pinch the stem back to a leaf node where at least one axillary bud is present, as these buds will ideally grow out to form new shoots. Cut or pinch flower spikes back to a leaf node as they appear. Coleus flowers are light purple or blue and develop at the ends of shoots. Pinching off flowers before they bloom and go to seed saves the plant energy and encourages vegetative growth.

Do you wish that your crape myrtle bloomed more than once? You can make it happen. Use pruning shears and cut an inch or two behind the dying flower cluster. The plants will think it forgot to make seeds and produce another round of blossoms. I use a 3-foot stepladder and a walking cane to pull branches toward me so that I can makes the cuts. Do not consider doing this if your crape myrtle is high above the ground. Your mother didn’t raise a fool.

This story was originally published June 28, 2017 at 6:47 AM with the headline "Is your wisteria getting a little aggressive? Here’s how to make it do what you want."