Will American Wisteria Plants Work for an Arbor Cover?

Arbors

• Keep the mature size of American wisteria in mind when buying or building an arbor. Although American wisteria isn't as aggressive as non-native varieties, it is a rambunctious, heavy plant that reaches lengths of 20 to 30 feet with vines as thick as small tree trunks. A lattice trellis or other flimsy support won't do, as the vine will likely overpower the trellis. Use a sturdy arbor with pressure-treated wooden support posts measuring at least 4 inches by 4 inches. Install the support posts 36 inches into the soil. Install two-by-four crosspieces using galvanized nails.

Training

• Once the wisteria vine is established, the weight of the plant will hold the vines in place. Until that time, use loose ties to direct the vine to grow around the vertical support posts. To create a cover, train the vine to grow horizontally when it reaches the top of the arbor. Once the vine is in place, remove the ties to prevent them from girdling the vine as it expands.

Pruning

• Wisteria is best pruned in midsummer. Remove long, wandering stems and untidy growth but leave the climbing vines intact. Cut new shoots by one-third to one-half their length to encourage short spurs that bear flower clusters for the next season. Avoid extensive pruning during the plant's dormant season, as aggressive pruning at that time results in out-of-control growth the following spring.

Invasive Potential

• Japanese wisteria (Wisteria floribunda) and Chinese wisteria (Wisteria sinensis), both of which grow in USDA zones 6 through 8, are aggressive plants that have outgrown their boundaries to become invasive in several areas. Unlike its non-native counterparts, well-behaved American wisteria is welcome in the garden and not considered an invasive plant. It still reseeds freely. To prevent unwanted plants, remove seed pods from the plant in fall and pull unwanted seedlings as they appear.