Wisteria is a beautiful flowering vine prized for its cascades of lavender, purple, or white blooms and sweet fragrance. This ornamental plant, however, also has a reputation for being an aggressive, nearly uncontrollable spreader that can quickly overwhelm a garden or landscape. The question of when wisteria becomes a weed depends entirely on its species and origin. Understanding the distinction between the different types of wisteria is the first step in knowing whether the plant in your yard is a cherished specimen or a destructive problem.
Native and Non-Native Wisteria Species
The aggressive nature of wisteria belongs primarily to the non-native Asian species: Chinese wisteria (Wisteria sinensis) and Japanese wisteria (Wisteria floribunda). These species were introduced to North America in the 1800s but quickly escaped cultivation. They lack the natural predators, diseases, and herbivores that keep their growth in check in East Asia, allowing them to spread unchecked across the landscape.
In contrast, the native American wisteria (Wisteria frutescens) is a far less vigorous grower, making it a suitable alternative for homeowners. The native species has shorter, more compact flower clusters that typically bloom later in the season. A key difference for identification is the seed pods: the invasive Asian varieties produce fuzzy, velvety pods, while the American species produces smooth, hairless pods.
Characteristics of Aggressive Wisteria Growth
The invasive Asian wisteria species earn their “weed” reputation through their rapid growth rate and destructive physical capabilities. These vines can easily grow ten feet or more in a single season, quickly covering arbors, fences, and utility poles. Over time, the stems develop into thick, heavy, woody trunks that exert immense pressure on supporting structures.
When the vine climbs into a tree canopy, it twines tightly around the host tree’s trunk and branches. As the wisteria vine thickens, it essentially girdles the tree, cutting off the flow of water and nutrients, eventually causing the tree to die. The sheer weight of the dense foliage can also snap branches and collapse pergolas or trellises.
Below ground, the root systems are equally aggressive, spreading widely and deeply in search of moisture and nutrients. This expansive root network can damage sidewalks, foundations, and compromise underground pipes or septic systems.
Eradication and Control Strategies
Removing an established invasive wisteria requires a multi-year commitment due to the plant’s robust root system and ability to resprout from fragments. Simply cutting the vine at the base is ineffective, as the remaining root crown will aggressively send up numerous new shoots.
Mechanical Control
A more effective mechanical approach involves repeatedly cutting the vine back to the ground every few weeks throughout the growing season. This starves the root system of energy. This method must be maintained for at least two to three seasons to exhaust the plant’s reserves.
Chemical Control (Cut-Stump Method)
For larger, more established vines, chemical control targeting the root system is typically the most effective method. The recommended approach is the cut-stump treatment, which involves severing the main vine about six inches above the ground.
Immediately after cutting, a concentrated systemic herbicide, such as a solution of 25% glyphosate or triclopyr, must be painted or dripped directly onto the fresh cut surface. Applying the herbicide within minutes is important, as the plant quickly seals the wound, preventing absorption. The herbicide is then translocated down into the root system, killing the entire plant. Homeowners should monitor the area diligently for root suckers or new seedlings for the following years. Treating any new growth promptly with a spot application of the same herbicide is necessary because any remaining root piece can regenerate a new vine.