Root Crown Excavation Wizardry

Originally published in TCIA Magazine.

The Zelkova tree looked rather poorly last fall. Portions of the canopy were thin and exhibiting early leaf drop. The leaves were small and off-color. The trend continued this spring. The new growth appeared anemic and sparse. I have suspected root issues with this tree, and removed stem-girdling roots (SGR’s) that were accessible near the surface. While parts of the root collar showed proper flare entering the ground, other areas showed no flare, entering the ground vertically. Additionally, these “flat” areas of the trunk seemed to coincide with the weakened areas of the crown. A root crown excava- tion (RCX) was clearly in order.

Although I see this problem with great frequency, selling a RCX to a potential client can be difficult. The irony is that it’s far easier to sell above-ground treatments such as pruning or fertilization, even though those treatments are likely to have little or no benefit to a tree with SGR or root-girdling root (RGR) issues. I suppose there’s something sexy about the aerial ballet of shiny bucket trucks and climbers to which blowing dirt around with a magic wand can’t compare.

This tree was strategically located to provide shade and aesthetics to a large horse barn. The owner is a well-educated lover of trees. She planted dozens of unusual trees on the property including amur cork, yellowwood, golden chain, sweet gum, katsura, and others. I had done several RCX’s to other trees on the property, with good results. Over time I have convinced her of the benefits of wood chips and proper (which sometimes means no) pruning. We do not fertilize.

The importance of this tree, along with a trust developed over the years, made the decision to do the RCX easy for this client. At best, we could reverse the demise of this tree; at worst, we would get a good sense of what’s happening underground and make informed decisions concerning its future.

We scheduled to do the job when there was a good deal of moisture in the soil. It was a cloudy, misty day. We set up plywood walls to contain the soil and fired up the pneumatic soil excavation tool. It did not take long to reveal the culprit. A root approximately 1-inch thick by 12-inches long was clearly embedded in the trunk, just below the flattened area. While the rest of the root system was growing in a spiral pattern, and clearly had issues, this root appeared to be having a direct impact on the vasculature. We removed this root along with other, lesser RGR’s, and replaced the soil. A thorough soaking was administered. Now we would wait and see.

We returned to the site three weeks later and were amazed at the results. The crown looked full, with good color and normal leaf size. I have seen good results from this treatment before, but never anything like this. The client thought me an “Arborwizard,” but I was doubtful. I checked with some fellow ASCA members to get their thoughts. While not unanimous, the consensus seemed to be that, yes, a direct correlation could be made.

In the words of Russ Carlson, RCA:

“Think about how the tree grows. The cells of the cambium divide and then enlarge. Once they reach a certain stage, the cell walls lignify and become rigid, at which point they can no longer grow larg- er. New cells grow in the now displaced cambium, next layer out. When the cambium has no room to expand, over time you have a series of small compressed cells, so sap transport is reduced. Now you come along and remove the obstruction. The cambium, which apparently was not dead, can grow without restriction once again. Those cells start dividing and the new ones can again grow to normal size. In just a few weeks in springtime, enough early wood can be created to make a big dif- ference in the sap flow to restricted areas.”

While I am sure that most RCX’s I have done have had positive effect, this by far was the most compelling. Timing is everything in life, and I am sure that had a big effect on this case, but the results cannot be denied. I have documented this case along with several others, and have used the images to encourage more RCX’s.

I still like my shiny bucket truck, fancy ropes, saws and saddles, but it is becomming clear that the air-excavation tool may be the most unassuming, revolutionary tool for saving trees to date.