In the past, tree surgery involved things like filling cavities with cement, installing re-bar and static cables, and even bolting trees together. Our understanding of trees as complex living systems has brought about more beneficial procedures and the old techniques are now used only as last measures.
The Comfort Maple Conservation Area on the Niagara Peninsula has a great example of where old school techniques on a 500-year old sugar maple have actually compromised structural integrity and shortened the projected lifespan.
When prescribing structural reinforcement techniques for your trees, our team of Certified Arborists and Qualified Tree Risk Assessors carefully consider Tree dynamics and Structural Risk Mitigation in deciding what should be done. Usually with a visual assessment and consultation on your trees, we are able to educate you on the need to save them or make them more structurally sound. The unfortunate part is that all trees are different and all severities of structural deformation have different degrees, saving them can be a costly investment.
More about the techniques
Cabling and bracing are the two most common forms of structural support for trees. They involve installing flexible cables (Dynamic Support Systems) or rigid rods (Threaded Rods) to reduce the chances of failure. Cables are typically installed high in the tree, at least 2/3 the distance from the defect to the union, and Crown rods are installed much lower, just above and/or below the defect. Cables are always a stronger alternative over rods because of their greater leverage and cables can be used alone, but bracing can be a compliment to cables. Other, less common forms of structural support are guying and propping.
When would you use such a technique?
There are three major uses of cabling and bracing: 1. Prevention – to reduce the chance of failure on a healthy tree with structural weakness, such as included bark, “V” crotch or union and or a cavity. 2. Restoration – to prolong the existence of a damaged tree, such as a tree which lost one of its main leaders in a storm and leaves the others vulnerable to further damage by wind and snow forces it may not be used to. 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.
The homeowner and the Arborist
Together, we need to consider a few questions first:
- Is this a reasonable treatment for the tree in question, or is it trying to preserve a tree that is actually nearing the end of its life?
- Can the cost of the procedure be justified for this single tree? Are there more pressing needs in the garden or in one’s personal urban forest?
- Is the tree healthy and capable of having enough sound wood to anchor to, or support the cable or prescribed dynamic support system?
- Is it understood that cabling is no guarantee that failure will not happen?
- Is it understood that the cable will need to be inspected annually, then replaced after 7-10 years?
What does the process look like?
First, have one of our Certified Arborists and Qualified Tree Risk Assessors assess the trees’ overall structural integrity and health. There are many signs we can see which are not always prominent or apparent and our experience can help with that.
Proper placement is the key to the installation of any of the recommended techniques. There are many important technical aspects to correct cabling and bracing and the first is the choice of hardware. What are the strengths of the hardware and what are the features, benefits and limitation in each circumstance? Where are we going to place it and in what configuration? Single, multiple, triangle or star are some of the ways we handle this
Our primary solution here at Arborwood Tree Service is the use of Dynamic Support Systems, things like the Cobra or Boa offer this. Trees are complex living organisms and they need to move and bend and flex in order to sense where they need response wood for strength. Much like leaving a tree staked too long, the tree doesn’t grow the necessary root for structure and stability. When a tree bends, flexes and moves in the wind, the symplast (just under the bark of the tree) creates a stimulus that in turn causes the tree to add response wood in the areas it needs. This is a huge benefit with our support systems as they help the tree achieve that and become stronger with elasticity and rubber inserts in the ropes. They are also less invasive and, rather than drilling into the tree and inserting lag bolts or through bolts, the dynamic support systems go around the tree and expand as the tree grows, therefore not girdling the tree either. If we install static or steel cables with bolts into the tree we take this ability away from the tree. However in extreme circumstances we will resort to bolts and rigid cables should the wounds or value of the tree warrant it.
Feel free to read more on the Cobra cabling system:More Articles ›