Wisteria season is here—but be careful which species you plant
These lavender blooms are a seasonal favorite, but some species can overtake trees and ecosystems. Here’s how invasive wisteria spreads, and what to plant instead.
In spring, wisteria vines explode into life, displaying large clusters of fragrant, purple flowers. This time of year the beloved ornamental garden plant typically blankets the entire Southeast United States, but can also be found as far north as Maine and as far west as the Pacific Northwest and California.
What wisteria lovers might not know is that species of the vine which came to the U.S. from China and Japan in the 1800s are impervious to local plant diseases and pests that might otherwise help regulate their growth. Left unchecked, exotic wisteria vines crush garden trellises and sheds under their weight and spread to nearby trees and forests.
These species are considered invasive in over a dozen states, including Maryland and Wisconsin, where it is illegal to sell Chinese and Japanese wisteria.
As the invasive vine kills off native plants, it could eventually cause erosion and other problems, says Georgia Department of Natural Resources plant biologist Eamonn Leonard.
“There's a level of ecosystem collapse that we probably don't know all of the implications of,” Leonard says. “As you start removing elements of an ecosystem, it's like rivets on a plane. At some point the whole thing's gonna fall apart.”
But it isn’t all bad news. American wisteria, or Wisteria frutescens, is native to the U.S., “tamer” than exotic wisteria, and a good alternative to plant in your garden, Leonard says. American wisteria has smaller clusters of flowers than the exotic varieties, but Leonard thinks the native vine is even prettier.
How invasive wisteria ended up in the U.S.
In the early 1800s, “it was very, very common for the horticulture trade to go out, find really pretty things, [and] bring them back,” says Rebekah Wallace, coordinator for the University of Georgia EDDMapS and Bugwood invasive species programs. That includes exotic wisteria, which came to the U.S. from China (Wisteria sinensis) in 1816 and Japan (Wisteria floribunda) about 15 years later.
“It's part of a larger story of that period of time,” Leonard says. Because parts of China and Japan have a similar climate to the U.S., people figured out that plants that grow well there would also grow well back home. So, they brought the exotic wisteria species to the U.S. and started planting them.
(How to fight invasive plants)
“I think it was also a mindset that native wasn't attractive back then, maybe, and that they were always looking for the exotic and the different,” Leonard adds.
Because American wisteria is native to the Southeast U.S. and the exotic varieties also grow well in that region, it became a symbol of the American South, draped across trellises and porches in a riot of color.
The ecological impact of invasive wisteria
Individual vines can grow up to 15 inches in diameter and climb as high as 65 feet. But though that might seem majestic for your garden, the vines are aggressive growers that can also strangle trees and overtake places where native plants once thrived, says Wallace.
Invasive plants like Chinese and Japanese wisteria are “just kind of bullies,” Leonard agrees. They cover tree canopies and prevent the sun from reaching plants trying to grow underneath. If the native plants can’t grow, wildlife might have less access to food and other resources they rely on for survival.
Wisteria can also kill entire trees, Leonard says. The vine wraps around trees “like a constrictor,” suffocating them.
(This floating flower is beautiful—but it's wreaking havoc on Nigeria)
In contrast to native plants—whose growth is naturally regulated by pests, diseases, and wildlife—Leonard says invasive species like exotic wisteria are free to grow without those other things keeping them under control. And the vines grow fast—as much as 10 feet per year.
If invasive wisteria is allowed to take over most of the ecosystem, it could ultimately restrict which wildlife, insects, and native plants are able to survive there, Leonard says.
Currently, state agencies like the Georgia Department of Natural Resources where Leonard works manage the invasive vine with a combination of herbicide spraying and controlled burning.
Should you plant wisteria in your garden?
If your garden already has exotic wisteria, it’s possible to maintain enough to prevent or at least minimize its spread. However, Leonard knows from firsthand experience that it takes ongoing effort. He had exotic wisteria in his yard as a kid that had to be maintained carefully.
Eventually, he replaced it with native wisteria, which he recommends as an alternative to the invasive varieties. American wisteria can still spread, but not nearly as aggressively as the exotic vines, he says. He has native wisteria growing on an arbor at his house that showed up in a different part of his yard one day. Exotic wisteria would have just destroyed the arbor entirely before moving on to other areas, he says.
(Where to find the first flowers of spring)
Wallace agrees that the native American species is the closest alternative to the Asian species of wisteria, but coral honeysuckle and crossvine are also nice options, depending on what plants will grow best where you live.
Leonard says in spring when plants like wisteria bloom is an ideal time for people to report any invasive species they come across on citizen science apps like iNaturalist or EddMapS.
“Hopefully that tide is changing [from people preferring exotic plant species] and people are starting to appreciate our native plants that have equal beauty and more value,” says Leonard.
