As practitioners of professional arboriculture, it is our goal to make decisions that lead to trees in our urban forest to be as healthy and safe as possible. When it comes to structural integrity of trees, we will never be able to eliminate risk or hazards completely. Yet, there are practices that we can do to mitigate structural risks which will not only prolong trees themselves from structural damage, but also protect people, property, and structures in our local communities.
We have worked with many property owners and managers over the years when it comes to large trees growing in high traffic or high-risk areas, such as near a home or structure. Specifically, many years ago we worked with a local homeowner on a tree in which they had concerns of large limbs from a silver maple encroaching on their home. In all situations, our goal is the safety of people and structures when addressing tree risks, however with large trees in good health, there are options other than large limb pruning to mitigate the risk. The other option is an application referred to as tree cabling. This practice involves installing appropriate hardware into a tree to improve structural integrity.
The thought process of an arborist in a situation like this is to balance the pros and cons of the two treatment options. When it comes to pruning large limbs (leads) from large, established trees, you are gambling on two fronts. First, the volume of living material being removed from the tree. Just like humans, as trees age it becomes harder to recover from significant changes. Removing a large portion of the living and productive vegetative material from the tree takes away energy production (leaves) which can lead to stress, compounding stresses to a tree can make it more susceptible to insect and disease threats. Second, is the tree’s ability to proper heal after the limb is removed. When trees are pruned, naturally or mechanically, they do what is referred to as “compartmentalization”. Trees don’t heal the same way that we do from an injury, they simply wall off or compartmentalize the area in which the wound occurred to prevent decay setting into the remaining living portions of the tree. Trees do this very well, but with a larger limb, lots of things must go correctly to ensure healthy wound healing. If the wound doesn’t heal correctly, decay can set it and lead a pathway again for insect or disease threats. Pruning large leads can also create an uneven balance in the tree canopy, making it an easier target for breakage in high winds or storms.
With the silver maple in this case with our client, the tree was very healthy and didn’t have any leading symptoms indicating decay or decline. With that assessment and weighing the risks of limb removal, our arborist came to the recommendation of installing a cable to support the structural integrity of the limb.
When cabling a tree, it is not installed to eliminate the risk of structural failure. Cabling is added support to reduce the risk of failure and most importantly to prevent catastrophic damage in the case of structural failure. If the tree does fail, the cable is a last line of defense to continue to suspend the failed limb so as not to hit structures below. Tree cabling in its simplest definition, is installing a metal cable into a large healthy stern and connecting to an opposite stern within the tree. Using high strength cable and anchors driven into each limb, they are connected and sized. This method of cabling will still allow movement for the tree in general weather conditions; however, during high winds or storms it creates a stronger tree, giving the cabled sterns the ability to withhold high winds and other weather conditions.
After the initial cabling of the silver maple, the tree held it’s limbs for many years, through some of our harshest midwestern weather. The tree continued to be healthy and of great aesthetic value to the home and homeowner. This success did not go unnoticed by the homeowner, until an even larger cabling success for them occurred in a recent windstorm in 2022. During the storm the limb that was of original concern separated at the main stern, throwing the limb from the tree. Instead of the limb crashing into their home causing immeasurable damage, the large limb held its connection to the opposite stern and only gently swept the ground. The cable had stayed intact to both limbs, swinging the broken branch away from the home and without any lawn damage. We did ultimately remove this tree, but having it’s life extended was a win for all.
This success story is twofold for tree cabling – the tree was able to live another decade with its added strength and allowed the homeowners to keep their beautiful silver maple. However, when the limb did fail, the cable served its secondary purpose perfectly; saving the home and property from additional damage. Tree cabling can be a great option for many trees with damaged limbs, large overhanging limbs, or to trees with intricate limb growth – but tree cabling is not a coverall for every tree concern. There are many options and alternative treatments that can be created to assure a healthy and stable tree.
Contact an ISA Certified Arborist if you have any concerns or questions about the strength and health of your tree. Staying proactive in the care of your trees will prolong their lives in our harsh urban forest and improve the natural aesthetic of our communities!