Over Trimming Trees
Mother Nature’s Moment - September 2020
by: Lesley Bruce Smith, ISA Certified Arborist
A tree that was not only “over trimmed”, but very badly trimmed, shortening its life by many years. Photos by Lesley Bruce Smith
Dr Alex Shigo, the father of modern arboriculture, once said: “Trimming your trees is one of the best things you can do for them, if you do it properly, and one of the worst things you can do, if you do it improperly.”
For a multitude of reasons we are seeing a huge number of trees that have been over trimmed or trimmed improperly. So what does that mean or what does it look like?
Although trees are single organisms, they have many little “communities” or branches that contribute to their overall health and wellness. Each branch provides food and increases the girth and strength of the tree at the point of their attachments. Many people hold the misconception that we can feed our trees via fertilization, which is like thinking you can help a starving person by just giving them vitamins. Every leaf on the tree is a food producer and is busily turning the sun’s energy into usable sugars for the tree’s sustenance. Trees must produce their own food, so when we trim them we should always be thinking: “How is this cut going to make this tree healthier and allow it to produce enough food to keep it robust?”
Arborists aloft making decisions about next steps
Obviously, we have many things to think about when we are trimming urban trees. We must consider human safety first, then property safety and tree health and safety. An arborist aloft needs to be always thinking about all these factors in the present moment and the effects in the future. In the present moment, she needs to consider her safety and that of her co-workers. She needs to consider how the cuts she is making will affect the ability of the tree to capture sunlight for creating its food. She needs to assess if branches are rubbing each other or against a house or other building. She needs to consider the structure of the tree and work to safely eliminate weak branch unions to mitigate potential future storm damage. She needs to evaluate how the tree will grow in response to her trimming today, and anticipate what she should do to insure the long term health and safety of both the tree she is trimming and the people that live with and around the tree. Not all tree trimming is created equal!
A Red Oak that was probably over trimmed because of the power line running through its middle, but it too has just had its life drastically shortened by this trim job. It also has made it much more vulnerable to failure, which when it fails, will take the power lines with it.
To insure trees are trimmed “properly” a tree trimmer needs to have years of experience and training to be adept at their job, to become a true arborist and then work towards ISA (International Society of Arboriculture) Certification. This requires not only learning about how to climb and trim safely while using dangerous power tools hanging many feet off the ground, but it also requires an in depth understanding of different tree species and their varying responses to trimming. Some of the ways we see trees being over trimmed is when a tree trimmer has not learned how to safely ascend to the outer branches of a tree and so they “hug” the center limbs and cut off all they can reach from the middle of the tree. This practice is referred to as lions’ tailing and essentially weakens the tree by removing many of the “little food producing communities” that provide strength. This creates trees that are weak and in the long term will be much more susceptible to storm damage. Weakening the tree also happens when too many branches are cut off the lower half of the tree or branches that are too large are removed. Lower branches lend beauty and strength to a tree and once removed will NEVER grow back in the same way. Large branch removal sets a tree up for rot and failure. Poor trimming is also exhibited when branches are removed with no understanding of how a tree grows or how it calluses over its wounds. Once a tree is wounded, and every cut on a tree is a wound, it will never “heal”. It can only callus over the wound attempting to wall off the area that has been damaged. So we need to have an understanding of tree physiology to make cuts that won’t create lasting damage.
Lastly, when a good arborist trims a tree properly, the natural beauty should shine through. A 250 year old native Oak tree can be destroyed in the space of an afternoon at the hands of careless trimmers. When a tree is lovingly and carefully trimmed it should look all the better for the attention.
For more information and specifics on this subject request our Tree Trimming Abstract.