Learn how to see the potential problems that may lead to a tree failure. Understanding the weakness may help you to make
the correct decision.
Tags:How to Identify Hazards in Trees,tree failure,arboriculture,arborist,Dangerous trees,hazardous trees,horticulture
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I’m often asked to inspect a tree, and the client asks me, what caused my tree to fail? My name is Blaire Glen, and I am an ISA certified Arborist. This particular tree failed during at storm, and many of the trees in the complex failed, so the question was, why do these trees fail when so many others did not? Was it just a storm that caused the problem? Or were there other weaknesses that led to the failures.
One of the key things that’s arborist need to do is understand when a tree is weak and what maybe the cause of the weakness, in this case this tree was topped in the past.
Here we have a recent topping of some red wood trees which is really criminal in my opinion, but the long term problems that are going to result from this, you can see there’s a lot of new growth and it going to develop multiple weak tops, instead of having one strong straight pole, the new tops are growing off of the edges of this old cut.
Sometimes a weakness is very obvious, this tree is destined to fail and I don’t know why it is still standing?
A lot of times we have to look at the structure of a tree, in this case we have a Modesto ash, and for all intents and purposes this tree looks fairly balanced. But if you look at the lower center of the picture, there is a crotch with the very, very tight inclusion.
When you have a situation where two branches grow too tight together, they actually end up pushing each other apart.
Here is a Siberian elm that has been repeatedly pollarded over the years, but it does not look like it’s been done for three or four years, so it’s become a massive big bush. Either we have some giant evergreen ash; you can see what happened here.
The new resulting growth off of a topped tree, it usually comes out as long straight shoots, now what you have to remember is that where this tress were topped ends up being a long term decay pocket.
So the subsequent new growth that is existing off of the old decay pocket becomes weaker as the decay gets worst in time.
Sometimes it’s difficult to identify when a tree has been topped in the past.
This is a Magnolia tree, and as you can see almost all of the branches are going straight up. That’s a good sign, that’s a good indicator that this tree had been severely butchered a long time ago.
Now to the untrained eye, there may not appear to be a problem with this branch, but what I see is this branch was cut severely just below the union there, and all of these branches are new suckers that have evolved in two larger branches. So their encapsulating in area of decay, there is also way too much weight as a result of the way this has re-sprouted.
Now the point of this whole topic here is not that we can trim these trees harshly and just keep up with then, but how to recognize when a tree was topped in the past and then allowed to re grow into a more natural looking structure, when that happens the weaknesses of these long limbs can sometimes be taking time bombs for a climber.
So we need to understand the strengths and weaknesses of the trees, how quickly they grow and encapsulate the old wounds and when you believe that you may have an area of weakness, you have to take the correct back up procedures when you have to climb in this trees, you have to double up your ropes, you have to be very, very concerned.
In the center if this picture, you can see a decay pocket in a few short years, that will become completely absorbed, but the internal decay wont go away, it will be inside and will still be rotting away. In time these tree will self-destruct.
Thanks for taking the time to view this presentation, and ones again my name is Blaire Glen and I am an ISA certified arborist.