By Jim Leser
We all know that trees provide many benefits including shade, wildlife habitat, cooling and wind protection for our houses, help in removing CO2 from the environment and of course the beauty they provide to our landscapes, community and forests. But did you know trees can pose a risk to us as well?
Risk is a product of the probability of a bad event occurring and the severity of its consequences. Two potential problems are damage to property and personal injury and indirectly, potential liability.
There are two methods to evaluate the hazard a tree poses, either quantitative and the one we can use, qualitative. While what follows may help the average tree owner improve safety, only a qualified arborist, certified in formal hazard assessment can make a definitive determination, especially when it comes to potential liability.
Regular inspections are needed. There is no excuse for ignorance. “Ignorance is bliss” will not stand the legal test, especially when dealing with public or community trees. There is only so much one can rely on an “act of God” defense.
What you should be looking for is primarily trees that have an imminent or probable likelihood of failure. Visual inspections should home in on the extent of trunk or large branch decay, general health of the tree, and its structure as it pertains to wind damage and cracking potential.
There are three important factors with the first one being target and likelihood of impact. A tree or its branches over a house, road, someone else’s property, and public spaces is more of concern than a tree in the forest. Frequency is also important. A playground or a park bench has more visits than say a day-only parking lot. And people are always more important than property.
The likelihood of failure based on the nature and size of the defects is a second factor. And lastly, consequences. The size of a tree or branch that might fail and fall has a great bearing on the exact impact it would have to the target.
So what should you look for? I would examine the tree’s crown, especially with trees that have notoriously brittle branches such as maples and willows. Also know that topping and “lion tailing” create weak branches. Crossing branches and excessively long branches are subject to breakage. And large dead branches are called “widow makers” for obvious reasons.
When looking at the tree’s trunk know that forks with narrow angles are subject to cracking and splitting. A leaning tree or one with an imbalance in the crown should be looked at closely. And any decay as evidenced by mushrooms and soft rot, as well as any cracks or large wounds should be a concern.
Last but not least is the root system. Anything that compromises the root system either obvious decay or trenching damage during construction can lead to catastrophic failure.
So what steps can you take to mitigate a potential hazard tree situation? You can change the target by moving benches and picnic tables to safer places and rerouting existing traffic patterns to avoid heavy pedestrian traffic near a hazard tree. Timely pruning and sometimes bolting or cabling can secure a potential failure point. Also avoid trees with thorns where children frequent, avoid blocking line of sight where cars are concerned and steer clear of power lines. I would also thin heavy fruit tree loads to avoid undue branch stress. And above all improve the health of the tree and remove dead or dying trees.
Never forget to evaluate your trees following storms with accompanying winds or heavy snow loads. It is always better to avoid hurting someone or causing damage to your property or your neighbor’s. This is your responsibility and the best way to avoid a legal liability problem.
Jim Leser retired to Cedaredge in 2007 after a career with Texas A&M University Extension in entomology. He is a member of the Cedaredge Tree Board and a Colorado Master Gardener.