How Does a Tree Root Barrier Work? Does It Harm the Tree?

The Deep Root Challenge

When planning a hardscape and/or landscape design, trees - and their wildly unpredictable root systems - can be one of the greatest challenges around which to plan.

So many factors influence tree root growth and the span the root system covers. Unfortunately, if left totally unchecked, this tree root growth could end up damaging, disrupting, or uprooting many elements of your design like sidewalks, curbs, driveways, septic, irrigation, in-ground lighting, landscape components, and more.

Fortunately, there is an answer to address this potential risk.

Deep root barriers for trees work by controlling the direction of tree root growth in such a way that the potential for those roots breaking through sidewalks or encircling and/or destroying other infrastructure or landscape elements, is dramatically reduced.

There Are 3 primary Types of Tree Root Barriers

  1. Root Traps or Screens

Root traps and screens are usually welded fiber sheets or woven fabrics that allow the roots to penetrate but retain and redirect them to a degree.

  • Root Deflectors

Root deflectors are made of plastic or metal. These types of barriers are typically most effective if they are at least .15mm. Their goal is to create a physical barrier that will contain the tree root growth fairly completely and direct it downward, deep enough so that when and where growth occurs, it is not disruptive.

  • Chemical Inhibitors

This type of deep root barrier is akin to root traps or screens but with an added chemical component—frequently Cupric Carbonate (CuCO3). Another common chemical used in chemical inhibitor root barriers is Trifluralin—a herbicide that slows root tip growth[1]. Obviously, the chemicals will break down over time, reducing effectiveness long-term.

But Do Deep Root Barriers Harm the Tree?

One concern many people have when discussing or considering tree root barriers is whether this root “manipulation” harms the tree in any way? 

Clearly, if we are integrating trees into the overall hardscape and landscape design, the last thing we want is unhappy or unhealthy (or especially, dead) trees.

There is a risk to trees if badly-designed root barriers are used or if the chosen root barrier is not installed correctly. One specific danger exists if the tree’s root growth is contained in such a way or to such an extent that it cannot or will not grow properly.

On the other hand, the general consensus among tree experts is that a well-designed deep root barrier, installed the right way, should not harm the tree in any way. Conversely, guiding growth around obstacles intentionally, may help to protect tree root systems rather than hurt them.

What Is Proper Deep Root Barrier Installation?

The proper deep root barrier installation process will depend on the root barrier chosen. Summarily, however, the important keys will be to:

  1. Ensure that the space allocated to root growth is wide and deep enough
  2. Install a deep root barrier that is tall enough in the ground to accommodate the tree’s standard root system
  3. Allow the root barrier to come above ground level a bit
  4. Pack the soil tightly around the barrier after it’s installed

For Sidewalk Shield, it’s also important to know:

The drip line of a tree is the outermost area that water is capable of dripping off of the limbs. Sidewalk Shield should be installed no less than half the distance of the mature drip line. For example, if the drip line of the tree is 10′ across, the Sidewalk Shield enclosure should be at least 5′ diameter. Not all planting areas are circular but Sidewalk Shield can accommodate by making a comparable growing area in rectangular or odd size areas. The ultimate objective is controlling tree roots but allowing enough space for tree health.

Learn More About the Specifics of installing Sidewalk Shield


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