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Is my tree dangerous? This is a question that can go through any tree owners mind, especially when you have children. It is a question that as an arborist you are often asked. Trees are living organisms that have evolved in a forest environment where it is okay to have branches fall over. They have not been designed in a way that other man-made structures have and do not come with a tested breaking strain.
In some cases it can be very obvious a tree is unsafe due to the presence of a significant defect. There are also some trees that in their present form represent a very low risk, such as new planting. The majority of trees however fit somewhere between these two extremes. This blog will help you understand why you might not always get a yes or no answer to the question “is my tree dangerous?” from an arborist and why you shouldn’t always trust it if you do. It will also give you some tips on what to look for in your trees to help you form your own decision.
An arborist can assess tree safety using the following
When assessing the question “is my tree dangerous?” there are a number of techniques an arborist can use. The most commonly used technique is visual tree assessment (a.k.a VTA). In VTA an arborist will look for certain tell-tale signs in a tree that can indicate dysfunction and a likelihood of failure. It takes training and a lot of experience to become proficient at tree assessment so it is important that you gain some information about the arborist who is looking at your trees.
VTA is a good method because it is very low cost and does not harm the tree in any way. Where VTA is lacking is that you cannot look inside the tree and this is where a fault might be hiding. A skilled arborist should be able to read the subtle clues a tree exhibits on both the surface and underneath the tree.
Methods for looking inside the tree have been developed but they can often involve making small holes in the tree which can breach the tree’s natural defenses. More recently non-invasive methods have been developed to “look inside” trees using sound imaging and heat imaging devices. However, environmental conditions can effect the accuracy of these methods.
Is my tree dangerous to the people around me?
Trees have evolved to break under certain conditions, if they didn’t break they would fall over, it is a survival mechanism. It is better for a tree that a branch breaks off in a strong wind or heavy snow than if it tries to keep hold of the branch causing the entire tree to fall over instead.
If a certain branch in a tree is using more energy for its growth than it is making via photosynthesis from its leaves it will likely die off because it is “too expensive” for the tree to maintain. These are just two examples of how trees self-manage. Both can lead to branches falling off the tree. They are natural processes that the tree undergoes all the time.
Common questions for arborists regarding tree safety
When you’re looking for the answer to “is my tree dangerous?” you want to ask the following questions. ‘How big are the branches, how likely are they to fall, and what will they hit if they do fall?” Determining these answers is not an exact science and so you will often hear an arborist talk about likelihood of risk rather than a definitive answer. The weather can play a very significant role in all of this too. For example a tree in perfect health will eventually fall in a tornado.
So, what can you look out for as a customer? Here are a few items which may indicate that you should contact an arborist:
- Fungal fruiting bodies (mushrooms) surrounding the tree or on the tree
- Look for changes in the ground surrounding the tree. Examples include cracks in the soil, mounds or hollows, excavations near the base of the tree, very wet or very dry ground.
- Movement at the root plate of the tree
- Loose or peeling bark
- Rot holes
- Branches that appear to be dead
- Branches without leaves during the spring and summer
- Broken branches
- Abnormally yellow leaves
- Lots of new shoots growing from the trunk of the tree
- It can also be good practice to have your trees looked at by a professional following any strong weather conditions.