Kristopher Criscione, Abdi, Damon, Fields, Jeb S.
Many of us have encountered a tree with a noticeably deformed root system. This often appears as woody roots that tightly wrap and circle the base of a tree trunk, oftentimes extending to just below the soil surface. This phenomenon is known as root girdling and is a common sight in urban landscapes. This undesirable feature is aesthetically unappealing and can have harmful effects on the health and development of the tree. The coiling roots can limit the flow of water and nutrients between the above and below ground portions of the tree, prevent outward growth at the base of the tree and decrease the stability of the plant.
There are several reasons why root girdling may occur in the landscape. One of the more common issues occurs during the transplanting process, when the root ball of a woody plant is installed too deeply in the soil. Roots require oxygen to convert the sugars received from the canopy into energy. This process is slowed due to the lack of oxygen available to the roots, as most of the soil-oxygen is near the soil surface. Similarly, there is generally more water and nutrients available in the upper soil layers. If the root ball is planted too deeply, roots may grow upwards in search of oxygen, water and nutrients. Oxygen availability issues can also occur when improper mulching practices are used. Incorrectly placing mulch in “mulch volcanoes” (i.e., mulch is piled near the tree base, covering the trunk) limits oxygen availability where the roots and the trunk meet. Other common reasons for girdling roots include when nursery stock becomes root-bound and encircles the inside of the pot due to the restricted space or when trees are transplanted into compacted soils.
Some visual symptoms of root girdling include small trunk diameter which can result in leaning or tilting of the tree; stunted growth; twig, branch or leaf die back; early leaf drop or early fall color; leaf scorch; cracks in the stem; or decreased resistance to abiotic or biotic stressors. However, these symptoms can also occur due to several abiotic or biotic stressors, such as weather patterns, nutrient deficiencies, drought, pests and diseases.
Figure 1: A severe case of root girdling.
Figure 2: Take the lopper to both sides of the root and line up the blade with the soil surface to make a clean, flush cut.
Figure 3: Use a handsaw for thicker roots. Gently saw the girdled root out, being careful not to harm the roots you wish to keep. Let the saw teeth do the work, there should be little pressure applied.