Those looping vines of purple-lilac flowers that looked so attractive this spring? Probably non-native wisteria—and proof that you cannot always judge plants by their showy flowers! These vines are extremely invasive, infesting roadsides, forest edges, and rights-of-way. They grow up almost anything in their path—limited only by the height of whatever they climb, with stems reaching up to 15 inches in diameter! They can shade out tree leaves, decreasing photosynthesis, and eventually killing the tree.
Wisteria identification
There are two Asian wisterias that have invaded most of the east coast and all of the southeastern United States: Japanese (Wisteria floribunda), which has lighter bark and twines counterclockwise around its host, and Chinese wisteria (W. sinensis) with dark gray bark that twines clockwise.
Management
Mechanical
For small wisteria infestations, remove entire plants, along with their roots and runners. Any root pieces left in the soil can re-sprout to produce new plants!
For more extensive infestations, cut climbing or trailing vines as close to the ground as possible. Although this may be labor intensive, it is a feasible control in areas where you cannot use herbicides. Cut vines back early in the season, and then every few weeks until the fall. This will stop growth of existing vines and prevent seed production. Remove wisteria vines from the bases of trees and shrubs to prevent girdling as the trees and shrubs grow.
Dispose of fruit, roots, and other plant parts in bags—not in the compost—to prevent re-infestation.
Chemical
The best time to apply an herbicide is in the spring and summer when wisteria is actively growing. Be sure to allow adequate time for the plant to regrow from the winter to ensure movement of the herbicide back into the underground portion.
Foliar application of a 2% (2.5 Ounces (oz) or 5 Tablespoons (Tbsp) per gallon of water) concentration of triclopyr with a 0.5% (0.5 oz or 1.25 Tbsp per gallon of water) nonionic surfactant is an effective control if you wish to use an herbicide. NOTE: If wisteria vines are growing up into trees or other desirable plants, you must pull the vines down prior to application of chemicals to minimize damage to the desirable vegetation. Do not cut the vines at ground level because the herbicide must move into the root system to provide better control!
If you must cut the vines at ground level, you can control the plants using the cut stump treatment method. Cut stems as close to the ground as possible and immediately apply a 25% (32 oz or 4 cups per gallon of water) solution of triclopyr to the stem. Wear disposable plastic gloves and se a disposable paint brush to apply the herbicide in order to ensure adequate coverage of the cut stem and minimize drift to desirable vegetation.
Native alternatives for Chinese and Japanese Wisteria
American Wisteria (Wisteria frutescens), native from Virginia to Missouri and south to Florida and Texas, is a clockwise twining deciduous woody vine that grows to 40 feet or more. It has fragrant, pea-like, lilac-purple flowers in drooping 6-inch long racemes that bloom in April-May after the leaves emerge but before they fully develop. This is an excellent vine for freestanding arbors, pergolas, posts, trellises, fences or terrace walls, but do NOT allow it to grow up desirable trees and shrubs!
Other native plant alternatives:
Hummingbird favorites:
• Coral honeysuckle (Lonicera sempervirens)
• Crossvine (Bignonia capreolata)
• Trumpet creeper (Campsis radicans)—this one can sucker and holds on with adhesive disks that can damage siding, so plant where it can spread away from your house!
Butterfly host:
• Dutchman’s pipe (Aristolochia macrophylla)—Host plant for pipevine swallowtail butterflies
Article by Bob Wardwell, Extension Master GardenerSM Volunteer
For more information:
Wisteria sinensis, Chinese Wisteria:
https://articles.extension.org/pages/62675/wisteria-sinensis-chinese-wisteria
Postemergence, Non-Selective Herbicides for Landscapes and Nurseries
https://content.ces.ncsu.edu/postemergence-non-selective-herbicides-for-landscapes-and-nurseries
As the vine twines:
http://www.namethatplant.net/article_asthevinetwines.shtml
Native vines for butterflies:
https://www.wildlifehc.org/10-native-vines-to-attract-butterflies/