Root barriers are continuous or interlocking sheets of plastic, metal, rubber, or other resilient-yet-flexible materials that are vertically installed from the just above the surface of the ground downward. The intent of a root barrier is to redirect trees’ lateral root growth away from streets, sidewalks, foundations, and other similar infrastructure.
There are several different types of root barriers on the market that vary in thickness, depth, and design (some are even impregnated with herbicide… yikes!) but the claims are similar—that root barriers reduce infrastructure damage by tree roots.
Turns out, reviews on that are somewhat mixed. There has been limited scientific study on the effectiveness or root barriers, and professionals’ experience with them is variable across cities and landscapes.
Here’s the arguments for and against root barriers:
Root barriers are relatively simple products that, when correctly installed, can prevent or at least delay damage to adjacent hardscape by tree roots. They are relatively inexpensive and can save money by deferring potentially expensive costs of removing offending trees or tree roots and repairing or replacing hardscape. As a result, root barriers protect infrastructure and extend the life of trees.
Tree roots may grow deeper than root barriers, allowing roots to grow under the barrier and back to the surface on the other side to cause damage. Root barrier effectiveness is influenced by the adjacent tree species, soil conditions, distances between trees and barriers, the root barrier type and how well it is installed, and other confounding factors that make success or failure difficult to predict. Root barriers come at a potentially unnecesarry cost to purchase and install.
So which side of root barriers are you on?
To be completely wishy-washy, there is not likely a right or wrong position on this. Both arguments are well-reasoned and well-intended. Whether you choose to install a root barrier or not might depend on your budget and your risk tolerance for potential conflicts between trees and hardscape.
Here are a few tips to guide your thinking on this issue:
- Proper installation is imperative. Root barriers will almost always fail if not installed correctly.
- Root barriers are best installed on new sites for new plantings. Retrofitting can be done but may require additional steps such as root pruning.
- Select a root barrier without herbicide in it. This is an unnecessary stress to the tree.
- Put as much distance between the trunk and the root barrier as possible.
- Deeper root barriers are probably more effective in the long-term. If you’re already going for it, might as well go all the way, right?
- Consult your local arborists, horticulturalists, and other experts. Their insights on local conditions and experiences with root barriers in your area are extremely valuable.
- Do some additional homework of your own. The following resources can tell you more:
Journal of Arboriculture and Urban Forestry: A Review of Root Barrier Research
Michigan State University Extension: Reducing Damage Caused by Tree Roots
Deeproot Green Infrastructure Blog: Will Root Barriers Harm Trees?