Root Barriers

We’ll be talking about transplanting trees, root pruning, and root barriers on Monday, July 16th, 2012*.

Root barriers can be used to protect underground utilities in locations where space is limited. Photo: UF Laura Sanagorski

Large trees in Palm Beach County provide beauty, habitat for wildlife, and shade to keep residents cool and utility bills low. A downside to managing large trees in urban areas is that sometimes we see root conflict with utilities, sidewalks, and other fixtures in the landscape.

Root barriers are a useful solution to root conflicts with sidewalks and utilities. They are often installed vertically to prevent root penetration and redirect root growth. Palm Beach County horticultural professional who do not provide this service may consider adding it to their list of offerings.  For professionals who wish to subcontract root barrier installation, certified arborists can be located with the International Society of Arboriculture’s search function at treesaregood.com.

Root pruning is conducted and a narrow trench dug between the tree(s) and the sidewalk, driveway, or utility conflict. It is important that care be taken with this step, as major root pruning can compromise the structural integrity of a tree.  After the trench is dug, either a chemical or physical root barrier is installed. A chemical root barrier is a piece of fabric embedded with an herbicide that stops root growth (often trifluralin). A physical root barrier deflects and redirects root growth. Prefabricated models are generally made of an interlocking hard plastic with ridges that direct growth downward. Both types of root barrier are available from one foot to four feet in depth. Root barriers can be installed using a linear or circular configuration. Linear installations are most common and may run along a sidewalk or utility trench. Circular configurations are used to contain the root balls of newly planted trees.

Conflict between root sand hardscapes is common in urban areas. Root barriers may be a solution. Photo: UF Laura Sanagorski

Conflict between roots and hardscapes is common in urban areas. Root barriers may be a solution. Photo: UF Laura Sanagorski

A final type of root barrier is sometimes referred to as three-dimensional, and is made of gravel. A layer of gravel under a sidewalk can be used to stop root growth and protect sidewalks. The gravel ensures that air pockets remain under the sidewalk. Since roots cannot grow through air pockets, sidewalks remain intact, and roots continue growing below. Research has found each of the types of root barrier to be effective, but some preference has been shown to gravel, three-dimensional root barriers.

It is important to remember to strive to plant the right plant in the right place to avoid major root and hardscape conflicts, although this isn’t always an option. By choosing trees that can reach their full size in the space available, we can avoid future conflicts.

*(This program is the third of eight in the 2012 Strengthening our Community Tree Canopy Series‘ for professionals, a project supported by FDACS and the Florida Forest Service through a 2011 Urban and Community Forestry Grant.  To learn more about upcoming topics in this series, Download the 2012 Urban Forestry Brochure here.  CEUs available for  ISA, pesticide applicators, FNGLA, and LIAF).

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