November 28, 2017
What is Tree Cabling and Why is it Important?
By Jessie McClellan of New Urban Forestry in Athens, GA
Trees are phototrophic organisms, which means they can “choose” to grow wherever there is the most available light. Because of an abundance of light in an urban environment (oftentimes directly over your home) this can often mean that some tree species exhibit a pattern of limb growth we arborists call overextended. You will see these limbs extending beyond the canopy of large shade trees, often locally in our red and white oaks and pecans.
These overextended limbs grow to a point where they can no longer support the weight of their canopy. In addition, trees that were not previously pruned or trained for good structure when young can exhibit V shaped crotches, or codominant stems, that have weak branch unions, often with included bark (another arborist term which explains the presence of bark embedded in the branch union). We have all witnessed the aftermath of a large limb failure on a beautiful old water oak and wondered if is this common, or that must of been one heck of a storm, or I sure hope that doesn’t happen to my tree.
Why can’t I do it myself?
Certified Arborists evaluate trees for health and structure and propose tree management work to meet specific goals, including tree preservation, risk reduction, aesthetics, and increased vigor and health. Arborists recommend cable installations to preserve the tree and to protect property or people, perhaps even with the goal of protecting the dairy goat in the barn out back.
Flexible steel cables are installed to add supplemental support to specific limbs to maintain the integrity of the tree and prevent damage to property. The goal of installing a tree cable, or cables (there are trees in Athens with as many as 9 cables), are intended to restrict movement of tree parts , or specific tree limbs, to aid in supporting new loads, such as new annual limb growth, wind and rain (we all know that song), and ice and storms.
Some common issues that might require cabling are: long heavy branches that are too heavy or overextended for the tree to support, branches that have weak branch unions over homes or other structures, and codominant stems that are structurally weak that if failure were to occur would likely damage your favorite neighbor’s Porsche.
So why not just prune the tree?
Pruning can reduce likelihood of failure and should be considered first as a viable option, but overpruning, or pruning without proper knowledge and technique can also cause significant damage to trees. In the recent past we often just removed the large limb in question for fear that it would fall on grandma. Unfortunately, we now know and are are largely concerned with the significant decay that now exists in the tree as a result of a large wound created by “pruning.” The last available option to reduce risk is to remove the tree. Over pruning, or trimming (another of my favorite terms — remember, folks trimming is what we do to the grass and bushes) can also negatively affect the health of the tree. Though we should always consider pruning first for good structure, cabling is recommended for supplemental support in limbs where pruning may be less effective, or the consequences of failure are significant both to the tree and to the whatever would be crushed if the limb were to fail, including grandma’s house.
Why can’t I see the cable?
Cables are installed high in the tree and often can be difficult to see from the ground. If you are not there to witness the cable installation and to see first hand our gloriously attractive arborist climbers at work, don’t be surprised if it might not be possible to see the cable. Make sure to ask one of the crew members (if you dare) to point it out for you, or pirouette across the newly installed line, the next time they are working at your property if you are unsure of where the cable is. You can also call Shawn. He will be happy to visit and assist with cable visualization.
And now the small print:
Cables should also be periodically inspected. It is recommended to have a CERTIFIED arborist visually inspect a cable annually and perform a climbing inspection at least every 5 years. Cables can be good for 20-40 years, but should be inspected to determine the integrity of the hardware, cable, and tree parts. A growing tree may need a new cable installed for better leverage in the future. A certified arborist (please call New Urban Forestry!) who is tree risk assessment qualified can perform a tree risk assessment to determine if cabling would benefit your trees, or your grandma’s tree, or your goat’s barn, or your neighbor’s porsche (or prius) .
LINKS
http://www.umass.edu/urbantree/factsheets/35codominantstems_rev1.html
http://www.isa-arbor.com/
