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Learning to Read Trees
by Tim Walsh, CTSP
As part of the job briefing, we must identify all hazards associated with the work before we begin (ANSI Z133.1 -2006 3.1.4, Annex A). Specifically, we need to perform a "visual hazard assessment" prior to working in or on a tree (ANSI Z133.1 -2006 8.1.1).
 A key point to a visual hazard assessment is knowing what you are looking at. The more experience that you have with trees, the better you will understand what is happening inside by looking at the outside.
This month we have been asked to remove a birch tree in someone's front yard. Depending on the angle from which you view the tree, the defects are more or less obvious. For the sake of learning, let's make an assumption that you only get one view (Picture 1). What would the four marks on the bark indicate? Let's take a closer look at the top mark (Picture 2). Does this closer look help out? Does it tell you any more about what is happening inside?
 Now let's cheat a bit and look inside (Picture 3). The marks were made, many years ago, when someone put a series of threaded rod into the tree to keep it from falling on the house. In this case we were lucky, in a sense, that the tree had split enough to show us the internal hardware. Many times the tree will close the wounds and the only way to know what is there is to be able to read the outside of the tree.
Lastly, we will give you a look at the whole tree (Picture 4). This view clearly shows the defect and the target, but we don't always have this opportunity to see inside the tree. We have to learn to read the outside to tell us what is on the inside.
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