Saturday 26 November 2005

Basic Cable

Recently I had the unfortunate opportunity of witnessing the destructive power of nature. A weakly attached branch in a large maple tree had broken away in hurricane winds, speeding towards a parked car below. Before the limb was able to hit its unfortunate target, the support cable that had been installed high in the tree restrained the limb and it was left dangling, still attached to the tree. This hundred dollar cable prevented thousands of dollars worth of damage. The homeowner who had lived in the house for many years didn’t even know the cable was there. It had been installed by a previous owner who had the forethought to have a professional come in and assess the likelihood of branch failure and take action. This cable extended the usable life of the tree by ten years and limited the damage caused by the branch failure.

Determining weather or not to install hardware into a tree can be a complicated decision.

Typically cables are installed to limit the movement limbs that appear to have a weak connection to the main trunk. They may also be installed to support weak or decayed crotches or co-dominate stems that have included bark. Stems of trees that are of similar size growing together with bark in between them can fail under extreme conditions. Wind, rain and ice are just three such extreme events.

No one would suggest that you should put safety cables into branches that are obviously dangerous or are sure to fail. An improperly rated or improperly installed cable may give you little more than a false sense of security.

Before you rush out to the local hardware and grab a spool of cable, consider the following. Will your tree benefit from the installation of a cable? Will the tree still pose a significant hazard to its surroundings once the cable is installed? Will the tree still contribute to the aesthetic environment of your yard? Tree cabling is a skilled enterprise, not only from the physical demands of installation, but also to know when and what cabling is appropriate. Each tree has its unique growth habits and structural qualities inherent in the wood. What is an acceptable practice in an oak may be hazardous in a pine. Cables and hardware must be specifically designed and rated for use in trees.

A properly installed cable located two thirds up the length of the limbs will help to reduce the risk of branch failure. Cables should only be installed if they will reduce the risk of failure to an acceptable level. As a professional I always make it a point to tell a client that a safety cable only reduces the risk of failure and does not eliminate it. Buy identifying a potential hazard in a tree you assume liability to properly address the situation. Many times cables are installed after a limb has shown signs of stress or is cracking. It’s important to remember that trees don’t heal wounds or cracks, they simply grow over them. The defect remains and may fail later. Trees don’t regain their strength and no longer need the support of a cable. Cables are a permanent installation and require maintenance. Cables should be inspected at least every three years to make sure they are still in good condition and serving their purpose.

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