The Cause, Assessment, Symptoms and Treatment of Stem Girdling Roots (SGR’s)
Urban landscapes are filled with trees that are planted too deeply. When root systems of trees are planted as little as six inches to several feet below the soil surface, they are buried too deep. These roots are unable to support the nutrient and water needs of the tree. In effort to survive, trees often create new roots from trunk tissue at the soil surface. These roots are called epicormic roots. They serve to keep the tree alive by acquiring nutrients and water.
Epicormic roots do not provide structural stability for the tree and are prone to bending, often growing in a circling pattern. If the roots grow close enough to the tree trunk they will compress the sapwood and eventually cut off the flow of water and nutrients. This disorder is called Stem Girdling Root Syndrome (SGR) and is one of the primary causes of tree decline in urban landscapes. Without treatment, SGR’s will eventually prove fatal to the tree.
Assessment and Treatment:
Prevention is the best solution, but for trees already planted, early diagnosis of visible symptoms is essential for future tree health. Trees without a visible root flare at soil level are symptomatic of the disorder and are at risk to develop roots that may girdle the trunk. Diagnosis can also be based on tree species. For example, maples and lindens are more prone to the disorder than are oaks.
To assess the situation, root excavation is necessary. An Air-Spade® is used to blow debris and soil away from the base of a tree, exposing the root collar. This evaluation determines the possibility of improving a trees’ condition. If it is determined that problematic roots may be safely treated, surgical cuts are made to the roots impacting trunk growth. It may be necessary to leave some offending roots, as only roots that do not affect tree stability and structure will be removed. There must also be enough roots left intact to provide sufficient nutrient/water uptake. If tree stem compression by girdling roots is too severe, removal of the tree is the only option.
Symptoms of Stem Girdling Root Syndrome
No visible root flare at soil surface
Tree trunk looks like a telephone pole going into the soil
The trunk appears pinched at soil surface
Tree canopy is thin or sparse
Die-back in upper canopy
Leaves are smaller than normal
Leaves may be off-colored (yellow)
Trees exhibit early fall color and leaf drop
Trunk is flattened on one or more sides
Sun scald or frost cracks visible on the trunk
Wilting or scorching of leaves
As trees stressed by girdling root syndrome are more vulnerable to other problems, special care should be taken to: