The Use of Supports To Reduce Risk Of Tree Failure
Tree cabling involves the installation of hardware that is intended to reduce the risk of catastrophic failure. Support cables are used to reduce tree damage by limiting the lateral movement of branches and increasing the weight that a supported branch joint can sustain.
Cables are installed in trees to provide support to weak or potentially dangerous limbs by connecting two or more limbs together. Mechanical support may be needed due to split, decayed or poorly structured limb junctions or the inherent dangers of weak-wooded trees. Poorly structured, multi-stemmed trees are more susceptible to breaking under the stress of wind or the weight of accumulated ice or snow. It is important to keep in mind that support cables have limitations.
Mechanical devices cannot be relied upon to make a potentially hazardous tree safe; once a defect is present there is always a risk of tree failure.
Before installing cables in a tree, the tree should be properly pruned and its structure evaluated. Hazardous and dead limbs need to be removed. The wood must be solid and large enough to support the cables. Trees that are too severely damaged should not be cabled, as a false sense of security may be created.
Multiple cables are often recommended to maximize strength; ideally, triangles or boxes should be formed between cabled leads.
The installation of cables in a tree represents an ongoing responsibility. All hardware in trees should be inspected annually to ensure proper placement and manage adjustments. All cabling systems should be updated or replaced after 7-10 years.
Dynamic and Static Cabling Systems
Arborists have two options for cabling trees: dynamic or static support systems.
Dynamic cable systems
Dynamic systems allow a tree to continue moving unrestricted unless the tree encounters high winds. The benefits are; that the tree continues to strengthen around the weak location, creating “reaction wood”, and no damaging drilling is required.
Guardian splicing wand
Static cable systems are best utilized with trees that are cracked, are in imminent danger of failure, or are too heavy to be supported by dynamic cables. Static systems use a steel cable that is stronger than a synthetic fiber cable and will constantly give support to the weak point. The problems encountered with the static system are invasive drilling, permanent rods or bolts, and a lack of strengthening wood tissue formation.