Tree roots naturally seek moisture and nutrients, which can unfortunately lead them to invade sewer lines, lift sidewalks, and compromise building foundations. Managing this growth requires a blend of preventative planning and reactive control measures. The goal is to establish a healthy landscape while protecting underground infrastructure and hardscapes from the expansive force of tree roots.
Preventing Growth Through Strategic Planting
Preventing root problems starts with making informed choices before planting any tree. Aggressive, water-seeking species, such as willows, poplars, and silver maples, should be avoided near structures. Instead, select trees known for non-aggressive root growth, such as Japanese maples, Kousa dogwoods, or certain dwarf fruit tree varieties.
Appropriate spacing is a major factor in preventing root conflicts with structures. Smaller trees should maintain a distance of at least 10 to 15 feet from a foundation, while larger trees should be planted at a distance equal to their mature height. For septic systems, the recommended buffer zone can range from 20 to 50 feet, or up to 100 feet for highly aggressive species.
Watering practices significantly influence a tree’s root structure. Shallow, frequent watering encourages roots to stay near the surface, increasing the risk of pavement damage. Conversely, deep and infrequent watering encourages the root system to grow vertically, making them less likely to migrate toward shallow sources of surface water.
Installing Physical Root Barriers
Physical root barriers block or redirect root growth using a vertical wall. These barriers are typically made from durable, high-density polyethylene (HDPE) or polypropylene materials, which are rigid enough to withstand root expansion. Barriers work by either blocking the root’s path or using vertical ribs to deflect the root downward into deeper soil strata.
The barrier must be installed to an adequate depth, typically ranging from 24 to 48 inches, depending on the tree species and soil type. Installation involves digging a trench wide enough for the barrier to be placed vertically between the tree and the protected structure. The barrier must extend one to two inches above the soil line, which prevents roots from growing over the top and circumventing the defense.
Barriers can be installed linearly, such as along a sidewalk or foundation, or in an encircling pattern around a newly planted tree. When using multiple barrier panels, sections must overlap by at least 12 inches to prevent gaps. This forces roots to establish a deeper, less destructive root system.
Using Chemical Control Methods
Chemical agents offer a targeted method for eliminating roots that have already infiltrated enclosed spaces, such as sewer and drain lines. The two main types are copper sulfate crystals and foaming root killers. Copper sulfate acts as a contact herbicide, releasing copper ions that kill the root mass upon absorption.
When copper sulfate crystals are flushed, they only affect roots submerged in the wastewater flow at the bottom of the pipe. This method is inexpensive and readily available, but it is a short-term fix that can potentially corrode metal pipes and harm beneficial bacteria in a septic system.
Foaming root killers, which contain the herbicide dichlobenil, provide a more comprehensive treatment. These products are mixed with water and expand into a dense foam that fills the entire pipe, coating all root surfaces, even those above the flow line. This offers a longer period of protection than copper sulfate, though application requires restricting water use for several hours to allow the chemical to work effectively.
Remedial Action for Existing Damage
When root intrusion has already caused a blockage or structural damage, remedial action is required. For clogged sewer lines, mechanical augers use a flexible cable with a cutting head to bore through the root mass, temporarily restoring flow. Hydro-jetting is a more thorough method, using highly pressurized water streams to cut through roots and scour the pipe walls clean of debris.
For roots damaging hardscapes or foundations, structural root pruning may be an option. An arborist must assess the tree before any cuts are made, ensuring no more than one-third of the tree’s root system is removed in a single session. Pruning should be done with sharp tools to make clean cuts, avoiding any roots within the structural root plate—the area near the trunk that provides stability.
If the tree is severely problematic, complete tree removal and stump grinding become the final solution. Tree removal eliminates the source of the roots, and stump grinding is necessary to destroy the remaining root collar and surface roots. Grinding the stump several inches below grade allows the area to be recovered with soil or new plantings.