Wisteria is an ornamental vine celebrated for its dramatic clusters of fragrant, lavender, or white flowers that cascade in the spring. The plant is known for its vigorous and aggressive growth habit, allowing it to quickly cover large structures and landscapes. The three main species cultivated are the Chinese (Wisteria sinensis), Japanese (Wisteria floribunda), and the more restrained American Wisteria (Wisteria frutescens). Its powerful growth above and below ground requires careful consideration before planting.
The Structure of Wisteria Root Systems
Wisteria develops a root system characterized by deep penetration and extensive lateral spread. It establishes a deep, woody taproot that can extend down to 10 feet in well-drained soils, primarily serving to anchor the massive vine and seek deep water sources. This depth varies based on local soil composition and moisture availability.
The vine produces a vast network of woody lateral roots that spread aggressively. These roots often remain relatively shallow, concentrating in the top 12 to 18 inches of soil, and can spread up to 30 feet from the main trunk in older specimens. The native American Wisteria’s root system is less aggressive than its Chinese and Japanese counterparts.
Identifying and Addressing Structural Damage
Wisteria’s aggressive growth leads to significant damage to built structures. Below ground, the roots are strongly attracted to moisture and nutrients, making them a threat to underground infrastructure. Wisteria roots penetrate and widen hairline cracks in sewer lines, septic tanks, and drain fields, causing severe blockages and costly repairs.
The lateral roots are the primary cause of damage to hardscaping. As these woody roots expand, they exert immense pressure on sidewalks, patios, retaining walls, and driveways, frequently causing them to heave, crack, and shift. While healthy, modern foundations are generally resilient, the roots can exploit existing fissures or weak points in older masonry or concrete, slowly forcing their way in and widening the gap.
Above ground, Wisteria vines grow by twining tightly around supports. The resulting pressure as the trunk thickens can crush or deform weak structures. The sheer weight of a mature, woody vine, combined with the twisting pressure, is known to damage wooden arbors, tear off gutters, and pull down less-sturdy trellises. Runners can also creep into small gaps in siding or roofing, growing thicker over time and potentially leading to water ingress and structural compromise.
Strategies for Root and Vine Management
Managing wisteria’s aggressive growth requires a proactive and consistent approach. To protect nearby structures, plant Wisteria a significant distance, ideally 15 feet or more, from foundations, underground pipes, and septic systems. Where closer planting is unavoidable, install a heavy-duty root barrier, preferably to a depth of at least three feet, to divert lateral roots away from vulnerable areas.
Aggressive and frequent pruning is the most effective method for controlling the vine and limiting the energy that fuels root expansion. Established wisteria should be pruned twice a year: a hard pruning in late winter and a lighter pruning in mid-summer to cut back the long, unruly shoots. This practice maintains a manageable framework and concentrates the plant’s energy on flower production rather than vegetative growth.
If removal becomes necessary, the process is challenging due to the woody root system’s tenacity. Cutting the vine back to the ground and grinding the stump is often the first step, but the plant will likely resprout from the remaining root network. Systemic herbicides are a final resort, applied directly to the freshly cut surface of the stump or main trunk to allow the chemical to travel down into the root system for complete elimination.