Wisteria is a popular, fast-growing woody vine admired for its spectacular, fragrant spring blossoms. This vigorous growth leads many to question its invasive potential and capacity for causing damage. While the vine’s reputation is largely earned by its aggressive above-ground growth, the root system is also powerful and requires careful management. The invasiveness of the roots stems from their sheer spreading force and density, posing significant risks to nearby structures.
The Anatomy of Wisteria Root Systems
The root structure of a mature wisteria is robust, supporting a massive, woody vine that can reach heights of 60 feet or more. The root mass is characterized by a dense network of woody, lateral roots that spread extensively near the soil surface. These roots are not typically a deep tap-root system like those of large trees, but they are powerful and grow quite thick over time. Older plants may develop roots that extend several feet deep for stability and water access. Wisteria roots rapidly colonize the soil, multiplying the vine through vegetative runners that sprout new growth far from the original plant.
Specific Risks of Structural Damage
The primary risk posed by wisteria roots relates to their lateral spread and relentless search for water. As the roots thicken, they exert lateral pressure capable of lifting and cracking paved areas like sidewalks, driveways, and patios, and compromising the structural integrity of retaining walls built without deep foundations. A more concerning threat is the infiltration of underground utility lines and drainage systems. Wisteria roots are strongly hydrotropic, readily entering small cracks in older, compromised sewer or water pipes. Once inside, the roots proliferate, forming a dense mass that causes blockages and substantial damage requiring professional repair.
Distinctions Between Wisteria Species
The aggressive reputation of wisteria is primarily driven by the Asian species: Chinese wisteria (Wisteria sinensis) and Japanese wisteria (Wisteria floribunda). These varieties are high-vigor growers, quickly reaching 60 to 80 feet in length. They are the species most commonly associated with overwhelming landscapes and causing structural issues due to their sheer biomass and rapid spread. In contrast, the native American species, such as Wisteria frutescens (American wisteria), offer a much less aggressive alternative. American wisteria typically reaches a more modest height of around 30 feet and possesses a significantly less vigorous root system.
Controlling Aggressive Root and Vine Growth
Managing an established, aggressive wisteria requires consistent intervention focused on both the vine and the roots. Regular, heavy pruning, ideally twice a year, is a fundamental practice to reduce the plant’s overall size and the nutrient demands on the root system. For new plantings near vulnerable areas, installing a physical root barrier is a proactive measure to divert lateral root growth; these barriers should be made of a thick, non-degradable material and installed to a depth of at least 24 to 36 inches. When completely removing a plant, the entire root crown must be physically dug out or chemically treated. Applying an appropriate herbicide directly to the fresh cut surface of the stump is the most effective method for killing the remaining root system and preventing regrowth.