Written by John Sepulveda, Certified Arborist WI-1454A and Patrick Walsh, Certified Arborist WI-1108A
Stem girdling roots occur when the roots of a tree or shrub begin to circle the trunk and start to cut
off carbohydrate flow from the leaves to the roots. The lack of photosynthates (sap) reaching the roots can cause a slow decline and ultimately, death of the plant. Red and sugar maples, along with lindens, American beech, pines, oaks, poplars, and elms are among the trees that commonly develop girdling roots. Trees suffering from girdling roots may only live 20% of their natural life. Girdling roots weaken the tree and open it
up to pests and disease that can speed tree death.
Recognizing the Signs of Girdling Roots
Sometimes, girdling roots will grow above ground, making it easy to recognize the problem. However, this is not always the case. Signs of girdling roots can be found by looking in the canopy, and may appear as a thin crown, or die-back of twigs and branches on the sides the roots are girdling. Another sign is flatness or less flare on one side of the tree trunk. Severe girdling can cause a tree to lean due to uneven growth and poor root development.
How to Prevent Girdling Roots
The best treatment for girdling roots is to prevent them before they have a chance to grow out of control. When planting, untangle roots that are circling. The planting hole should be loosened so that the roots can penetrate into the surrounding soil. The tree should be planted at the proper height and mulched correctly so as to not encourage unusual root growth. Avoid heavy foot traffic and machinery near the root flare and around to the tree to minimize soil compaction.
Girdling Root Treatment
The best way to stop a root from continuing to girdle a tree is by removing it. The first step in removing stem girdling roots is removing the soil or turf around the base of the trunk to expose the roots. We remove this top layer using an air spade, which is a tool that uses pressurized air to safely remove material around the base of the tree without damaging the finer fibrous roots.
Once the area has been carefully excavated an arborist can locate roots that are currently girdling the base of the tree as well as roots that may cause future issues. Pruning the roots is similar to pruning branches; clean and precise cuts are made to ensure proper healing and re-growth. In severe cases a tree may need this treatment done in phases over the course of a few years. The removal of problematic roots needs to be measured as to not create stress or structural damage.
Once the roots have been pruned the area is backfilled. This process removes the stem girdling roots but at the same time aerates the soil around the base of the tree. In instances where removal of girding roots is not possible palliative treatments in the form of fertilization, growth regulators or root invigoration are available to help extend the life of your tree.
Improving the Condition of the Soil
The air spade can also be used for therapeutic treatments to improve soil conditions around the tree. The vast majority of trees in the urban landscape are dealing with poor soil structure, namely compaction, which increases the density of the soil. Compacted soil creates resistance that prevents roots from growing freely. Highly-compacted soils restrict water from moving down through the soil. This water saturation in the upper layers leads to oxygen deficiency where most of the tree's roots are located.
To amend compacted soils we use the air spade to break up the top layer, without damaging the roots, to introduce oxygen and organic matter to the root zone. In areas where the lawn is a concern we employ a technique called vertical mulching. The arborist will plunge holes in the ground, similar to lawn aeration, throughout the root zone. The holes are then filled with organic matter. Vertical mulching can help alleviate compacted soil without disturbing the lawn surrounding the tree.
Hoppe is a full-circle tree care company celebrating its 50th year of excellent service to southeastern Wisconsin customers. We have a team of certified arborists and plant health care technicians on staff to provide expert tree services, from planting to pruning to prevention and treatment of insect and disease issues. If you would like an inspection of your trees or are considering planting new trees in your yard, give us a call at 414.257.2111 to schedule a visit by a Hoppe certified arborist.