A ninety-five mile per hour wind whips through the thick branches of an ancient oak tree. It seems that every gust has the potential to finally bring down this giant and historic tree. However, the wind is fighting a losing battle. The old oak has been retrofitted with a system of cables and supports that prevent the tree from succumbing to high winds. This is the work of Bill DeVos, an arborist who founded the company TreeWorks. DeVos’ company has been employed nationwide to help preserve and improve the health of old and large trees. DeVos gave a presentation about his life’s work at the Vermont Tree Stewards Conference in October.
DeVos spoke about many of his most difficult projects, ranging from protecting a historic Buckeye tree on the University of California Berkeley campus, to transplanting over 2,000 large oak trees on a golf course in Georgia. Each of these projects is unique, but DeVos approaches each with the same mindset: he will do whatever it takes to save a big tree.
After speaking about these projects, DeVos took his audience outside to demonstrate some of the tools his company uses to assess the health of trees. The first tool shown was an air spade. This machine uses compressed air to remove soil around the roots of trees. This technique inflicts less harm on the roots than a tool such as a shovel would. The point of removing the soil is to get a better view of the health of the root system. One of the most important things to look for is the presence of girdling roots. These are roots that have grown around the main stem of the tree and prevent the flow of nutrients and water between the roots and the canopy. If girdling roots are present they can be removed by cutting them with a hammer and chisel.
Another tool DeVos uses is called a resistograph, which measures the structural health of the tree. This tool drills a long, thin needle into the trunk of a tree, and produces a graph of the resistance the needle encountered. The resistograph reveals the strength of the wood, as well as any weak or hollow spots in the tree. This information guides DeVos in determining the amount of structural support the tree will need.
Also presenting at the conference was Andrew Pleninger, an urban forester from Rochester, New York. Pleninger wrote the book “The ABC’s Field Guide to Young and Small Tree Pruning”. Pleninger walked his audience through the basics of his book, and then took us outside to demonstrate the correct way to prune a tree.
The most important aspect of pruning is to make sure not to do too much. Never cut off more than one third of the canopy of a healthy tree. If the tree is unhealthy, cut even less. Before starting to prune, decide whether the tree is an A-form tree or a B-form tree. An A-form tree has a clear central leading stem. If one looked at the profile of an A-form tree, one would be able to draw a straight line from the top of the tree to the bottom. A B-form tree does not have a central leading stem, and a line drawn from the top of the tree to the bottom would take several turns. If the tree is an A-form, prune the tree to encourage the growth of the main stem. Perhaps Pleninger’s best piece of advice was that one should not think of what the tree will look like in the future. Focus on what the tree looks like at the present time, and prune in accordance with its current state.
As someone who is interested in big trees, I am very appreciative of the work that DeVos and Pleninger do. DeVos is a mastermind at saving trees, and without his work many historic and record-setting trees would not be standing today. The work that Pleninger does gives small trees more potential to grow into healthy, large trees. By communicating their techniques to the public, these men have given Vermont’s tree stewards the knowledge and skills to encourage the growth and health of big trees. Thanks to their presentation, the Vermont Big Tree Program will certainly see new record-setting champion trees in the future.
Author: Sam Gersie, UCF Intern