Cabling and Bracing
Cabling and bracing are the two most common forms of structural support for trees. Trees can grow in such a manner that their physical structure can no longer support their own weight. This is particularly common in mature multi-stem trees and trees with open canopies. Failure of a large branch or stem can result in property damage, personal injury or the decline of a tree's health. Cables and bracing rods are tools arborists use to protect or improve the structural integrity of a tree.
Cabling and bracing consists of installing flexible cables or rigid rods to reduce the chances of failure of defective unions. Cables are installed in trees to provide support to weak attached limbs by connecting two or more limbs together. Cabling is most often used to support a tree canopy with a structural defect or over stressed, where mechanical support may be needed due to split, decayed or poor limb attachment or the inherent dangers of weak-wooded trees. Poorly structured, multi-stemmed trees are more susceptible to breakage under the stress of wind or the weight of accumulated ice or snow.
Cables are installed high in the tree, at least 2/3 the distance from the defect to the crown. Rods are installed much lower, just above and/or below the defect. Cables are always stronger than rods because of their greater leverage. Cables can be used alone, but bracing is always supplemented with cables. Other less common forms of structural support are guying and propping. Guying is used on healthy trees whose roots are not holding.
Here is an example of a codominant leader tree failure, which tends to happen more often than others, especially in storms, and would have been a good candidate for bracing and support.
There are three major reasons for cabling and bracing:
Prevention: To reduce the chance of failure on a healthy tree with structural weakness;
Restoration: To prolong the existence of a damaged tree;
Mitigation: To reduce the hazard potential of a tree.
We offer three types of cable support systems:
Dynamic systems allow a tree to continue moving unrestricted unless the tree encounters high winds. The benefits are: The tree continues to strengthen around the weak location, creating "reaction wood" and no damaging drilling is required.
Static cable systems are best utilized with trees that are cracked, in imminent danger of failure or too heavy to be supported by dynamic cables. Static systems use a steel cable which is stronger than a synthetic fiber cable and will constantly give support to the weak point.
Brace rods are intended to provide more rigid support for weak unions created by co-dominate stems or included bark.