Tree roots are naturally programmed to seek out sources of water and nutrients, which often leads them toward residential infrastructure. They can cause costly damage to sidewalks, driveways, foundations, and underground utility lines. Controlling this expansive growth requires a strategic combination of preventative measures and targeted interventions to maintain property integrity and landscape health.
Proactive Prevention Through Strategic Planting
Controlling root spread begins with careful planning before a tree is placed in the ground. Selecting a species with a non-aggressive root system significantly reduces the risk of future structural conflicts. Taproot-dominant trees, such as Oaks, Pines, or Hickory, send their main roots vertically downward, making them less problematic for nearby surface structures than shallow, laterally-spreading species like Maples or Willows.
Beyond species selection, establishing a safe planting distance from existing infrastructure is paramount. Small to medium trees should be planted at least 10 to 20 feet away from underground utility lines and pipes. Large species that mature over 40 feet tall may require a separation of 40 to 60 feet or more from overhead power lines to prevent canopy interference.
Implementing Physical Root Barriers
When planting near existing structures cannot be avoided, installing a physical root barrier is necessary. These barriers, typically constructed from high-density polyethylene (HDPE) plastic, fiberglass, or geotextile fabric, act as a solid underground wall. They function by redirecting roots downward or laterally away from the protected area, rather than stopping growth entirely.
For the barrier to be effective, it must be installed to a sufficient depth, typically a minimum of 30 inches. Depths of 1.5 to 3 meters may be necessary in expansive clay soils where roots grow deeper to seek moisture. The barrier should also extend a few inches above the soil line to prevent roots from growing over the top edge. Proper placement involves installing the barrier 1 to 2 meters away from the foundation or area being protected, ensuring the tree retains adequate root volume for stability.
Chemical Treatments and Inhibitors
Chemical application provides a targeted method for controlling root growth within sewer lines where mechanical removal is challenging. The two primary agents used are copper sulfate and dichlobenil. Copper sulfate crystals can be introduced into the pipe, where they contact and kill the small, fine roots that have infiltrated cracks or joints.
Dichlobenil is a potent growth inhibitor applied in a foam that expands to coat the entire pipe interior, ensuring contact with roots entering at the top of the line. Both chemicals are considered non-systemic when used correctly, meaning they only impact the roots they touch inside the pipe and do not harm the entire tree. Confirm with local authorities whether copper products are permitted, as they can sometimes pose an environmental risk to wastewater treatment systems.
Safe Root Pruning and Removal Techniques
When roots are actively causing damage, mechanical pruning is a reactive measure that must be executed with caution to preserve the tree’s health and stability. Cutting large structural roots too close to the trunk can severely destabilize the tree and open it up to disease. Avoid cutting roots that are larger than two inches in diameter.
Pruning should occur no closer to the trunk than a distance equal to three to five times the diameter of the trunk. For example, a tree with a 12-inch trunk diameter should not have roots cut closer than three feet away. Root pruning is best performed during the tree’s dormant season, and all cuts should be made cleanly with sharp tools to promote rapid healing and limit the potential for decay. Any major root removal should be preceded by a consultation with a certified arborist to assess the tree’s overall stability.