Wisteria is one of the most beloved ornamental plants as high climbing vines and cascading flower clusters.
The downside is that wisteria vines can be difficult to get rid of, and some species are aggressive spreaders.
There are four major species you’re likely to plant, which may be grouped into American and Oriental varieties.
American wisteria (Wisteria frutescens) and its sibling Kentucky wisteria (Wisteria macrostachya) have smooth seed pods and blossom after the leaves have appeared.
Chinese wisteria (Wisteria sinensis) and its counterpart Japanese wisteria (Wisteria floribunda) are more aggressive growers with fuzzy seeds and blooms that appear before the foliage develops completely.
Unfortunately, wisteria can spread easily if not well-maintained, both through seeds and their extensive root system.
This can turn a normally wonderful plant into a gardening nightmare.
Are All Wisteria Species Invasive?
Chinese and Japanese wisteria are highly invasive species of wisteria compared to their two US counterparts and also look slightly different.
You can identify Chinese wisteria by its clockwise twining pattern and gray-brown woody vines covered in fine white hairs.
Japanese wisteria has brown vines which twine counter-clockwise.
New plants have hairs on the vines which disappear as they grow older.
American wisteria has reddish-brown, hairless vines and also twines clockwise.
Kentucky wisteria’s vines are thinner and twine counter-clockwise.
Wisteria spreads quickly, and the seeds may be carried by wind or water over long distances.
These perennial plants can live for more than 50 years and send out runners which lead to more plants at runner nodes.
Chinese wisteria is considered the most dangerous, with more than 19 states in the Eastern United States declaring it invasive.
Common areas of infestation include ditches, forests, and roadsides.
What Damage Does Wisteria Cause?
Wisteria causes two major problems.
- It is toxic to many animals, including pets and horses.
- More importantly, wild vines will slowly choke trees, cutting into the bark.
- New growth can cut off sunlight to native groundcover and vegetation.
- This can lead to deforestation and the loss of native species.
How To Control or Kill Wisteria Vines?
Chemical methods tend to be the best treatment against both old growth and new sprouts, but even these will take time and dedication.
Complete, careful excavation of the area is perhaps the only way to truly kill wisteria naturally.
If you use an herbicide, be sure to wear rubber gloves and other safety gear.
Depending on the herbicide, it will either be applied using a sprayer or paintbrush.
- You can use RoundUp (AKA glyphosate) on wisteria in the fall once trees start turning.
- Cut back the vines down to about ground level and apply a concentrated RoundUp formula labelled for wisteria onto the freshly cut stump.
- You can double the effectiveness by adding the concentrated RoundUp to florist picks.
- Insert the picks into the ground so the tip punctures your wisteria roots, feeding poison directly into the plant.
A good brush killer such as Remedy Ultra will work over time against wisteria growth.
When herbicides don’t seem to be working after a reasonable amount of time, you may choose to attack climbing vines using similar methods to English ivy. Details on How To Kill English Ivy.
This involves mixing a small amount of diesel fuel to the herbicide, although this method should be used with reservation due to fire and environmental risks.
Another last ditch remedy that works but may harm surrounding plants is to peel the bark from the vines and paint commercial-grade bleach on them.
For obvious reasons, this method is a poor choice when working around other plants, as the bleach may contaminate the soil.