Having just returned from the annual North Central Texas Urban Forestry Conference this last week, I was reminded of the process of cabling and bracing trees. The reason that I was reminded of this type of work is that part of the curriculum of the conference was a class dealing with structurally defective trees and whether or not properly installed cabling and bracing is helpful to those plants.
For an arborist, it was a pretty interesting lecture with a lot of good practical information. I’m afraid that for the average lay person, it probably would have been a little dull. As usual for these kinds of classes, there was also some time spent on the latest installation methods and hardware.
One of the things that fascinates me about trying to hold trees together with metal and wires is the fact that this process is an attempted melding of a dynamic, living, and growing organism (trees) with a static, often rigid, unchanging, usually metal, mini-framework. With a little bit of thought, you can see how hard it is to wed these two incompatible things together into a successful, continually growing and changing tree.
As you can imagine, it didn’t take professional arborists very long to figure out that just randomly installing some bolts, cables, and chains in trees was both not very effective, and unreasonably expensive. Unfortunately, unprofessional arborists discovered that they could litter trees with parts and charge unsuspecting clients a lot of money for it.
Usually when arborists are talking to clients about installing hardware in trees, we normally don’t make a distinction between cabling and bracing, but other than the fact that they are both artificial means of strengthening trees, they are two different things.
Cabling is when attachment points are installed on branches and then some type of chain, cable, or rope is run between these artificial tie ins so that the connected branches can share structural stress and mutually support each other. There are a lot of different ways to correctly install cabling, and there are many more ways to incorrectly install it.
When I see cabling that is incorrectly installed, the most common mistakes are either in the height of the installation, the attachment points, or the size of the hardware. Properly installed tree cables should be approximately two thirds of the way up the branch measuring from the base of the branch, not the height above the ground. As you can imagine, since it can be difficult to reach that spot in a tall tree and very awkward to work between two branches at that height, most cabling is installed much too low. When the cabling is tied in too low down the branches, the stress on the cable is greatly increased which if nothing else will result in early failure of the cables and/or attachments.
Attachments that are correctly installed should be drilled into or through the branches where they are placed. This allows the living cambium of the branch to continue to grow and pass nutrients into the canopy and allow photosynthate to come back down the branch from the leaves. Drilling holes through and placing hardware in branches two thirds of the way up the branch is exactly as hard as you think it is, so instead of the drilling, most people just wrap cable or chain around the branch instead. Wrapping something around the wood instead of drilling through it has an effect on the tree very similar to a tourniquet on the limb of a human being. When you see a tree that has been tied together by running chain, cable, or something else around the branches, you are looking at incorrectly installed hardware that is going to be detrimental to the health of the plant.
I often look at trees where the cable has broken, the attachment hardware has pulled out, or some part of the system has failed due to wear or stress. A lot of times, this is due to the fact that the hardware and cable used were to light duty for the stress they were subjected to or, and I think this is unfair to the customer, the installer put in material that would handle the tree only as it was on the day of installation. Since trees are supposed to grow and get larger, it shouldn’t take a rocket scientist to figure out that when the tree gets larger, the stress on the cabling is going to increase and that needs to be allowed for when it is installed.
Bracing is when bolts or very heavy cables are run through the trunk or the branch unions of the trees and tensioned so that there is little or no movement allowed at the installation point. I much prefer to brace if it will solve the problem. If applicable to the tree, and properly done, bracing has the advantage of being very heavy hardware that is a permanent installation which will should not need further work (more expense to the customer) a few years down the road. Additionally, as the tree grows and covers the ends of the hardware, the bracing will become partly or totally hidden.
Cabling and bracing are both expensive work that done incorrectly will be a large waste of money. When you are dealing with an I.S.A. Certified Arborist, you are talking to someone that has been tested and certified in this type of work, when you are talking to someone else, where did they get their training?
The next KWKC Green Team workshop titled Annuals and Perennials will be held at 2 P.M. Saturday, March 26th at Willow Creek Gardens, 1820 South Treadaway, in Abilene.