Unchain My Heartwood: Replacing a Tree Support System
Howard GaffinOriginally published in TCIA Magazine.
Something was amiss with that old oak tree. It just seemed wrong from the get-go. A long, open split ran down the main trunk from where a defective crotch had begun to fail long ago. There is no way this tree should be standing. What could be holding it together? I followed my gaze up the trunk and there it was. About 10 feet above the crotch, a contraption of seemingly medieval design embraced the tree. Composed of chain and pipe and nuts and rod and even a hook, this intriguing device had held this tree together for some time.
The improvised device was partially embedded in both leaders, and the effects of the stem girdling were evident in the upper crown. If the tree were to be retained, the device would have to be removed, and a new brace and cable system installed. There would be no guarantees that the crown would regenerate. Areas of decay were evident throughout the split trunk. It was questionable whether there would even be enough sound wood to allow for through-bracing.
I consulted with the owners of the tree. We discussed the pros and cons. We agreed that I would first perform an aerial inspection and determine if installing a support system was feasible. The inspection revealed a rather thin layer of solid outer wood in one of the stems. I was reluctant to proceed with the job, but the clients’ wish to preserve the tree coupled with a low target rating made the effort seem reasonable.
I took some photos and measurements, and then headed back to the office to do some research and design a system.
I whipped out my copy of the ANSI A300 standard (Part 3) – 2006 Supplemental Support Systems (includes Cabling, Bracing, Guying and Propping) and began to scheme. Here’s the neat thing about being an arborist: It’s a science and an art. On occasion, you really have to think. There are many excellent guidelines and best management practices (BMPs) available to arborists. The problem is that treatments for trees, as with people, often need to be customized to the individual. From whole tree removals to transplanting, unique challenges are constantly presented. Good improvisational engineering skills are the foundation and delight of many a successful arborist.
In this case, best management practices BMPs suggest that at least three rods, 3⁄4 inch in diameter, be installed, along with at least one cable above. The lack of substantial solid wood eliminated the possibility of “dead-end bracing.” Budgetary constraints, along with the tree’s architecture, necessitated a compromise with the BMPs. A 30-inch auger bit would be sufficient for most of the holes, but the site above the crotch would require at least a 48-inch bit, and the cost of a 4-foot-long, 13⁄16 auger bit was a budget breaker.
I was, however, able to find a reasonably priced 60-inch-long, 11⁄16 auger bit. As the crown above was not excessively heavy, and there was no target below, I elected to do some end-weight reduction pruning and install four 5⁄8-inch rods along with two support cables. It could be argued that more rods should be installed, but I felt that four would be sufficient, or at least closer to industry standards than the device currently employed.
One problem I have run into when drilling through large diameter trees is accuracy. I don’t have to tell anyone who has tried to drill a straight and level hole with a 3-foot or longer drill bit the difficulty involved. I rigged a jig to install in the tree to help align the drill bit.
I chose a calm, comfortable day to do the job. We laid out and organized all the tools and materials needed before we left the shop. Fortunately, we were able to access the site with a bucket truck, reducing the difficulty involved. We devised a plan and set out our tools.
The two leaders were no longer in alignment where the split had occurred, but there was no way we could correct that. We would install the braces first, starting with the lowest, then the cables, and lastly, remove the medieval device. I set up my improvised jig and proceeded to drill. I was somewhat anxious as the limits of my 3⁄8-inch electric drill were about to be challenged. Slowly but steadily, the sharp new drill bit bored smoothly into the tree. I stopped frequently to clear the shavings. The drill was clearly straining, but appeared to be up to the task.
The jury-rigged jig was helpful, but as a prototype there was, alas, room for improvement. None of the holes were exactly where I wanted them, but three had satisfactory alignment, and the fourth was still positioned well enough to employ. The rods went through with ease. Bark was excised where the washer and nuts would meet the wood. The nuts were tightened, excess rod removed, and we were ready to install the cable. The tree architecture above allowed for the installation of two cables, approximately two-thirds of the way up from the split, which fit in well with ANSI guidelines. The defective crotch made dynamic cable sys- tems inappropriate for this tree. I elected to go with 1⁄2-inch, forged eyebolts and 1⁄4-inch EHS cable. I installed a temporary 3⁄8-inch poly line from point to point to mimic the cable and help align the drill holes.
The cabling proceeded without incident and the moment of truth was upon us. Usually, when replacing a previously installed support system, retaining the original is considered a good choice if possible. That would not be an option in this case. The vasculature was being compressed. I called for the angle grinder equipped with a diamond tipped blade. The chains of tyranny would soon be van- quished!
I donned my helmet, face shield, safety glasses, ear protection, heavy gloves, steeltoed boots, Kevlar vest, and lucky underwear. The embedded chain turned cherry red as the blade progressed. I braced myself at the moment of release and then... nothing. There was nary a move- ment in the tree as the contraption dangled below me, indifferent to being rendered obsolete. I continued to work at removing the chain from the wood tissue, achieving moderate success. I performed a crown cleaning and light crown reduction as the sun set, casting a rose colored hue on the surrounding wood and canopy.
We returned to check the tree about three weeks later. A new child’s rope swing hung from a stout lower limb. The upper crown looked OK, and I thought, maybe we had gotten to this in time.
I have to commend the current stewards of the property. The old oak offered no substantial benefits other than wildlife and aesthetic appeal. Several other mature trees were in the vicinity. My initial response upon viewing it was removal, which would have been far less costly than installing an adequate support system. The tree owners surprised me with their request for preservation, and reinforced a valuable lesson: One must strive for objectivity when consulting with clients. Offer different management options, without bias, to help them achieve their goals.
Back at the shop, we took a good look at the apparatus we removed. Naturally, being tree guys, we ridiculed and belittled it. But aside from the fact that it was girdling the stems, the design was actually thoughtful and effective (though I’m still a bit perplexed by the hook). Had it not been installed, that tree would be long gone, and I would not be writing this today.
Reader Comments (1)
You sometimes wonder how tree such as this survive when snapping in half is in their genetic programming