What is Root Girdling ?
Have you ever walked past a tree to admire its very interesting roots? Have you ever stopped to think about whether or not the tree was actually healthy? When a tree’s roots have nowhere to grow, sometimes they can coil up near the base of the tree, or even start to grow around the tree. This process is actually called root girdling, and it can be very damaging to the tree. Images to the right show some examples of trees that have girdling roots. The term “girdling” refers to roots that encircle, confine, or limit the growth of the trunk or other roots of the tree. Stem-girdling roots are roots that girdle specifically at the base of the trunk.
Root girdling can occur in many ways, one of the most common causes of root girdling occurs in nursery container grown trees. The roots grow until they run out of room, and then begin to curl in and around themselves. Poor planting techniques can also result in girdled roots. When trees are planted, the root ball must be loosened to allow the roots to grow in its new home. Too tightly packed soil, and too deep of mulch can also suffocate the tree and result in root girdling. Girdling can also be caused by straps, ropes, wires, and other man made materials.
What are the Consequences of Root Girdling?
As roots circle and engulf the trunk, they can severely damage the natural processes that occur within the tree by restricting its vascular transport. Stem-girdling roots do not cause a rapid decline of trees; However, after a sustained period of time, can lead to sudden failure during an environmental stress, such as a storm. Although it may take 5-10 years for the roots to fully suffocate a tree, they will slowly suffocate the flow of sap to the roots, halting a lot of nutrient production in the tree. The weakened transportation system will eventually not be able to provide enough water or nutrients to the tree, or the leaves. Trees that have suffered from girdled roots for a long time can also severely lean, or even break off. They are also more susceptible to insects, other infectious diseases, and natural environmental stressors.
Visual assessment by a certified arborist would be needed to be fully certain a tree’s roots are girdling. However, here is a list of visual signs that could tell you that your tree might be suffering from girdling roots:
How do you Treat Root Girdling?
Treatment of stem girdling roots is very dependent on the size of the roots that have girdled, and the age of the tree. Small roots that have girdled can be easily removed, or pruned. To properly prune roots, remove several inches of the root, ensuring it cannot reconnect with the tree. Pruning is commonly done with loppers, chisels, oscillating saws, and small chain saws. Larger roots that have girdled, it is in the best interest for you, your tree, and your wallet, to call a certified arborist. Removal of girdled roots that are larger than two inches in diameter can be a very involved process, and a certified arborist should be called to handle the job. Some root collar excavation may be necessary to see all of the girdled roots, and prune them. Roots that have been grafted to the tree are especially tricky and should be handled with extreme care by a certified arborist.
Keep in mind the long term effects that root pruning can have on the tree after treatment of the girdled roots. Removal of stem-girdled roots results in a net loss of a portion of the root system, and therefore a reduction of water and nutrient supply to the crown. Some trees may not be able to recover from severe root pruning as easily as other trees depending on their species, age, size, and a multitude of other factors that would be analyzed by an arborist. Removal of large roots that are close to the base of the tree also severely impacts tree stability. Some trees quickly develop adventitious roots that are able to provide immediate water and nutrient flow to keep the crown of the tree looking elegant, but even a light wind could make this tree fall over. Another approach to treatment of the girdled roots without causing failure of the tree would be to slowly trim back a few roots at a time, allowing other roots to grow back and maintain a safe yet achievable fix to the problem. An ISA certified arborist could work on this treatment plan with you, and work out a schedule of when to treat the tree.
Preventative measurements taken to prevent the development of girdling roots would be the most optimal option. Here are some tips to help you ensure your tree’s roots never girdle beyond the point of repair:
In conclusion, roots that have girdled around the tree begin to slowly suffocate the vascular transport of nutrients and water throughout the tree. This process is slow but can be very damaging to the tree’s health and stability. You should consult an ISA Certified Arborist before making any major decisions about what to do with your tree. Preventative measurements that can be made when planting the tree can be critical to the development of root girdling later in the tree’s lifetime.