After a recent high school reunion, I got together with a good friend I had not seen in many years. When I visited with him and his wife at their home in Sacramento, he took the opportunity to ask me one of those “well, since you are here, can you look at my tree?” questions.
I get a lot of those and I really don’t mind.
Sacramento is a great tree town, where shade is essential in the summer heat. Their home is on a quiet street populated with big shade trees. A huge ‘Modesto’ ash presides over their front yard, with long heavy limbs over the roof and street.
Typical of this tree variety, the trunk divides into several scaffold limbs about six feet above ground and the limbs have tight “V” shaped attachments to each other. At the location of the attachments the bark is pinched between two limbs, a condition called “included bark”.
Over time, as they grow in girth, the adjoining limbs cannot get a good grip on each other. There are two main reasons for this:
1. The included bark keeps them separated.
2. The limbs are “codominant”, i.e. roughly equal diameter. Neither one can get a good grip on the other. Stronger attachments form when a branch is 1/2 or less the diameter of the parent limb or trunk.
Meanwhile, the included bark gets pinched ever tighter, leading to death and decay of tissues and wood.
Standing on the ground, scanning the branch structure, I found a long tree cable, high in the canopy, attaching the two main codominant scaffold limbs together, and another, shorter one, attached to two other limbs. These are commonly installed to limit strain on weak attachments.
I asked, “When was the last time you had the cables checked?” He was not sure and thought it might have been quite a few years. Apparently, the tree service had not informed him cable systems need to be checked on a regular basis and adjusted or revised as needed.
I told him my standard recommendation is to have them inspected every three years after installation.
With the long, heavy limbs high above the roof, the potential for severe damage is increased because they would fall quite a distance, gaining momentum, before hitting the roof.
In this instance, damage can be prevented. In another instance, which I saw a couple years ago, the owner was in the dark about cable systems and tree defects until it was too late.
They had purchased a home with a huge tree in front. Apparently, it was never disclosed at the time of purchase, or simply not noticed, the tree had an old cable system that had been installed to protect a weak attachment of two huge limbs.
On a calm, late spring day, the tree fell apart and crushed a car. The load of thick masses of new leaves and shoots contributed to the structural failure, but the underlying cause was the weak attachment and the cable system that had become inadequate as the tree grew heavier.
As I surveyed the wreckage, I found a wire rope clamp type of cable attachment system. The cable had pulled out of a U-bolt style clamp.
Quoting the current, International Society of Arboriculture Best Management Practices for Tree Support Systems “Cable clamps (wire rope clamps, bulldog clamps) are not used in North America to form terminations on any cable larger than 1/8-inch diameter. They are used in the United Kingdom and Australia, however. Cable can pull through cable clamps under repeated shock loading…”.
This one that failed had 1/4-inch cable and it would have been an obvious problem to any Certified Arborist or Certified Tree Worker, if they had the opportunity to inspect the tree.
It raises the question: Shouldn’t it be a standard practice to have formal tree inspections when a sale is pending on a property with large trees?
Cable systems are easy to miss. When I was working for a tree service, I once had a customer ask me during a follow-up visit why we did not install the cable system that was part of the contract. I had to show him that it was, indeed, up there. You just need to take some time to look.