Wisteria Vines. Friend or Foe?

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Nothing captures the spirit of the South like Wisteria in full bloom, hanging gracefully from a trellis or gazebo. Wisteria blooms are fragrant, hanging in bunches like grapes, while the foliage offers protection from the summer sun. The vines grow rapidly, given something to climb on, and aren’t picky about soil or growing conditions. They attract lots of butterflies, bees and hummingbirds to your garden.

However, Wisteria is very destructive of wood structures. It will pry them apart, sending tiny tendrils into gaps and cracks, and under siding and downspouts. Before you know it the tender shoots grow into fat, woody vines strong enough to support the entire plant, and as they expand they will gradually tear apart all but the strongest construction. They will also choke trees like a boa constrictor, wrapping around them in a spiral and cutting off their circulation.

Wisteria needs a strong support to climb on until it gets old enough for the woody vines to support themselves. It prefers to climb on wire fencing or lattice, rather than smooth pipes (like lamp posts) or trellises. It will grow and bloom best in full sun, but will grow in dappled shade.

If I had to design-build a trellis for wisteria I would construct it like a chain-link fence stood on end; steel supports set in concrete below the frost line, with chain link or other strong metal mesh for the plant to grab. Not pretty, but the vine won’t tear it down and will cover it in short order. I definitely wouldn’t attach the trellis to a building, instead stand it a foot away so I could cut off any tendrils that want to take my building apart.

Established Wisteria vines grow very aggressively and need to be pruned back, or they will smother everything in their path. You can nip back the new tendrils during the season, but more importantly you should prune the plant during late fall or winter. Remove crowded side shoots and dead wood, cut off any suckers at the base of the vine, and prune the major branches back to about one foot from the main trunk.

Keep in mind that Wisteria is highly poisonous, so you should wear gloves while pruning. Keep stems and seed pods away from children and pets. Seed pods provide winter interest, however if you bring them indoors they will explode when they warm up.

Wisteria can take several years to get established before it will bloom. Seed-grown Wisteria may not ever bloom, or perhaps not bloom as heavily as a plant produced by grafting. Too much nitrogen, such as provided by fertilizers like 10-10-10 and Miracle-Gro, will produce fast growth but inhibit blooming. Newly planted Wisteria is very thirsty, but doesn’t need much fertilizer to perform well. To make sure your Wisteria will bloom, it’s best to buy a named variety. If you buy it during the bloom season you’ll know for certain what you’re getting.

Steve Boehme is a landscape designer/installer specializing in landscape “makeovers”. “Let’s Grow” is published weekly; column archives are online at www.goodseedfarm.com. For more information call GoodSeed Farm Landscapes at (937) 587-7021.

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