When a tree has a structural defect that poses a high likelihood of failure a support system can often be used to reduce the risk. Tree support systems are used to provide supplemental support to individual branches and/or entire trees. Cables, braces, guys and props all provide supplemental support by limiting movement. For young trees, pruning is the preferred method to eliminate structural issues. Pruning may remove structural defects or lighten the load on tree parts with high risks of failure. On larger and mature trees, the combination of pruning and a support system may reduce the risk of failure.

 

Cables restrict the distance that branches can move in relation to each other. Installed across a weak union, they will greatly reduce the risk of failure. Installed on over-extended branches, they can be used to support the branch. Cable systems minimally consist of a set of anchors (eyebolts), a cable, and the appropriate means of connecting the cable to the anchor. If the tree dictates a more complex system, more cables and/or brace rods may be required. Cables are installed high in the tree, a distance approximately 2/3 the distance between the weak union and the ends of the branches. 

 

Brace rods are threaded steel rods inserted entirely through the tree with nuts and washers installed on both ends. They are used to reduce the risk of two or more leaders spreading farther apart or moving sideways in relation to each other. They are also used to fasten together a union or branch that is split apart. When bracing trees, at least one cable is usually installed for added support. In cases where it is impractical to install cables, rods can be used alone, but the strength gain will be less than with a cable system.

 

Props are used under leaning branches or trunks when cables and brace rods will not provide sufficient support to reduce the risk of failure. Typically, props are used under parts that are nearly horizontal and close to the ground. Props can be made from wood, steel, concrete or other materials. The prop should be designed so as not to restrict future growth of the branch. On the ground side, the prop must be anchored in the ground so as to keep it from moving excessively. A concrete footing is often the preferred anchor. 

 

All support systems have a limited service life. Steel cables may last 20 to 40 years in an arid climate or with a slow-growing tree but, in an area exposed to salt spray or with a rapidly growing tree, cable service life could be much shorter.  It is highly recommended that a trained and experienced certified arborist perform yearly inspections on these structural support systems.