Tree Support Systems: Cabling in Action

With so much snow in the winter of 2016-17, the damage to trees throughout the city is evident. Mature trees in particular are at risk of sustaining broken limbs or toppling over.

During a recent bout of snow, we received a request to save a fallen Vine maple, an indigenous tree of both sentimental and aesthetic value to its homeowners. With a shallow rooting system, this particular maple was at high risk for failure.  It was decided that the mature tree could be saved using two basic support methods:  cabling and guying.

What is the Difference?

As outlined by theInternational Society of Arboriculture:

Cabling is the installation of a cable within a tree between limbs or leaders to limit movement and provide supplemental support.

Guying is the installation of a steel cable between a tree and an external anchor to provide supplemental support.

To Save a Tree

Tree support systems incorporate the three basic ideas of:

1. Prevention – to reduce the chance of failure on a healthy tree with structural weakness, such as included bark in a branch union. Included bark greatly weakens the branch union.

2. Restoration – to prolong the life of a damaged tree, such as a tree which lost one a main branch, leaving the others vulnerable to further damage by wind and snow forces.

3. Mitigation – to reduce the hazard potential of a tree, such as a multi-stem tree near a heavy traffic area or high target zone.

 Support System 1:  Guying

The first tree support method we used was guying. Installed two-thirds up the height of the Vine maple, a direct line ran from the maple to the supporting Western hemlock. Using the tree-to-tree system of support, the maple will become dependent on the hemlock for the remainder of its life.

Fallen Vine maple.

Before we could begin guying, the tree had to be winched back into its original spot. With a winch connected to the supporting hemlock, we hoisted the maple upright until the root ball was back in place.

Winching the maple back into position.

An anchor was then installed on each of the two supporting hemlocks, roughly 20 feet up the trunk. An additional two anchors were installed lower down on the Vine maple. The guy wires consisted of 1/4″ EHS- Extra High Strength- steel aircraft cable.

Anchoring to the Vine maple

Guying to the supporting hemlock

An eye splice (left, connected to Vine maple) and a dead-end grip (right, connected to hemlock).

 Support System 2: CABLING

Particularly common in mature, multi-trunked deciduous trees, trees can grow in such a manner that their physical structure no longer supports their weight. The weight of the canopy with an additional load created by winds, snow, or wet foliage may be more than a branch attachment can hold. Often, the result is limb failure.

This particular tree had suffered limb failure in the past, proceeded by a bad cabling job. Note: the wrapping of wire around the stem of a tree for an extended period of time will result in stem girdling.

A poor cabling job: the multiple wrapping of the cable around the limbs is abrasive and causes severe girdling over time. Proper tools are necessary to complete a healthy cabling job.

Proper cable systems minimally consist of a set of anchors, a cable, and an appropriate means of termination for connecting the cable to the anchor limb. Running from one limb of the tree to another, we installed 10 cables that joined at an O-Ring in the centre. The 3/16″ EHS air-craft cable reduces movement and stress on the weak points in the tree, yet still allows for give and branch movement.

 

Limb-to-limb cabling

The Result- a second lease on life

We hope that this Vine maple will continue to grow and thrive-  living proof that trees can be saved by certified arbourists using tree support systems. Your tree will thank you! 

To learn more about cabling,  visit the September issue our of Tips section.