Tree roots, although primarily underground and not visible, comprise a large portion of a tree's mass and are essential to tree health and safety. Roots anchor the tree, providing stability. They absorb water and nutrients, providing the essential elements for tree growth and survival. Roots are also a primary storage place for food (carbohydrates) produced by the tree.

    Root damage is common in our communities. Some damage occurs as a result of everyday activities, and some occurs during site development, building construction, and utility line installation and servicing. Common activities that cause root damage and death include:

> Compaction of soil with foot, vehicle, and equipment traffic and materials storage.
> Cutting roots by trenching for utility line installation or repair.
> Grade changes, including cuts and fills.
> Change in water drainage patterns and water levels.
> Removal of topsoil without replacement.
> Soil contamination from equipment washouts, vehicle and lawn maintenance chemicals.

    Root damage can result in an immediate effect on a tree, such as leaf drop, limb dieback, or leaning. Oftentimes, however, root damage takes 3 years or more to become visible, with crown dieback the most common symptom, and premature tree mortality a common result.

    Sometimes root damage cannot be avoided, but many times it can be minimized using new technology and equipment, such as the directional boring or the air spade. When tree roots are cut, they should be cut cleanly with a sharp pruning shear or saw. When root damage is severe or when one or more major woody roots are cut close to the tree, the whole tree should be evaluated to determine whether or not it should be removed. If a damaged tree is to remain, it should be monitored and maintained to promote tree health. Maintenance may include mulching, aeration, irrigation, or other activities as necessary.

     The City of Covington's Tree Preservation Ordinance requires that the roots of public trees be protected and that a "tree protection zone" be established during construction around these trees and trees retained on new commercial developments and subdivisions. This is a recommended practice for any community tree, whether publicly or privately owned.

     For existing trees, the tree protection zone should be at least the size of the tree's "critical root zone". The critical root zone is the soil area below ground, on the surface, and the space above ground defined by the tree's dripline. The tree's dripline is the greatest extent of the branches. Tree roots do not stop at the dripline, however, but generally extend out from the trunk at least two and often three times the extent of the branches. And, the majority of tree roots are found within the top 12 inches of soil.

     For small trees, newly planted trees, or trees with narrow crowns the area of the critical root zone is often too small for proper protection. Therefore, the recommended method of establishing a tree protection zone is to calculate a circular area above and below ground with a radius equivalent to the greater of 6 feet or 1.5 feet for every inch in trunk diameter at 4.5 feet above the ground.

     Remember that tree roots don't recognize property lines. It is very likely that public trees will have roots growing onto private property, and private property tree roots will be growing onto public property. Respect the boundaries of the tree protection zone and protect tree roots wherever they occur!

     For more information on protecting tree roots or the City's Tree Preservation Ordinance, contact the City of Covington's Building Safety and Zoning Department at (770)385-2178.

Prepared by Connie Head 01/04/2001