Anatomy of Future Tree Failure

Warning signs of tree failure in your own yard

As a International Society of Arboriculture (ISA) Certified Arborist in Richmond, VA, I am constantly looking at trees.  Although my specialty is preventing future problems at planting time, it is impossible to predict what a tree will do 20, 30 or more years down the road.  

Trees provide countless benefits to the world around us.  Especially in the urban and suburban landscape, where we tend to remove more trees than we replace.  Keeping good care of the mature trees that we retain in these challenging environments becomes very important.  However, there are times when we must look at a situation objectively and weigh the risks against the benefits. 

During hurricane Isabel, I was working for a tree service in Fredericksburg, VA.  In the days after the storm, I witnessed what large trees are capable of doing to houses and other property.  No matter what the construction methods, a house is not much of an obstacle to a tree trying to touch the ground.

As a matter of fact, I have had a tree hit my own house, so I know what it is like to try to remediate the damage.  Once a tree puts holes in the roof, the rain is free to come in, leading to extensive headaches in the future.  

So how can we know what a tree will do?  Is it possible to predict tree failure?  

Let me start off by saying that all trees pose some type of risk.  There is always an element of risk that comes along with such a large block of wood towering overhead.  

Tree failures during normal weather can be predicted to some extent.  We can analyze the conditions of a tree and the ramifications of failure and provide a recommendation to either attempt to repair the tree or replace it.  However, during a storm event where winds can exceed 60 MPH, there is no way to predict failure.  All trees are fair game at this point, especially if the ground has been saturated by rain preceding the event (Isabel).

So what do you look for?  How do you know if a tree is going to fail soon?  

this tree has it all and then some….

This is an oak tree that I happened by in the Byrd Park area of Richmond the other day.  The first thing you will notice is the huge tear on the trunk from about 5-10' above the ground.  This was (probably) caused by a co-dominant stem breaking off.  A co-dominant stem is a branch of a tree that is close to the same size as the main trunk.  When a stem of this size rips off, a huge wound is left, leading to (most likely) inevitable infection by various pathogens, insect damage, and further decay.  Lower branches of a tree also serve to distribute wind forces on a tree.  With only branches at the top, the twisting forces are multiplied further down the trunk.

Here is a closer shot of the damage down low.  As you can see, the damaged has progressed from a simple branch break to decay and rot down low.  A nasty wound like this that cuts into the tree trunk itself is almost always going to develop decay.

If you look higher up in the tree there is another co-dominant situation.  This is not a major warning sign, however, as there is a branch-bark ridge at the junction of the branches.  A branch bark ridge indicated proper attachment.  If you see a high angle junction like this with bark that appears to be included in the junction, look out.  That is almost one of the worst things you can see.  This isn't the case here, but this situation is not ideal.   High-angle attachments like this are just not very strong.  As the angle approaches 90 degrees (straight out) from the trunk, the strength increases.

mmm, dead wood

This is the margin of the damaged area near the ground.  The fungus that you see is a fungus that attacks dead tissue, but can also expand into living tissue as well.  When you see this fungus, there is a good chance there is dead wood present, with active decay eating away strong wood.

uh oh…

This is a fungus (most likely ganoderma or armillaria) that attacks the root tissue and bases of trees.  These fungi are two  of the "Big Three" as defined by the ISA ( I am not a fungi expert, but I am sure it is one of the two.  The exact diagnosis is in my view irrelevant).  While this is alone is not a cause for immediate removal, the presence at the base of a heavily damaged tree is a major warning sign of future failure.

mmm, more dead wood…a veritable buffet

Here is an even closer shot of the damaged area at the base.  Not the greatest picture, but if you look close you can see small holes, and evidence of insect boring.  Insects will burrow inside of the damaged parts of trees, and wreak all sorts of havoc.  Whether they are bringing a fungus with them, or laying eggs that will hatch and tunnel around in the inner parts of the tree, the result is the same.  Decay is introduced directly into the innards of the tree.

enough already!

As if all this was not enough, if you look up, you can see that there have been at least two major limbs already removed from this tree by the city.  Why that happened I don't know, but I would suspect that they broke further out from the trunk.  The city tree department does not just cut limbs off for no reason.  This would be another warning sign that this tree is prone to limb breakage.

This tree is a smorgasbord of warning signs.  Most of these by themselves would not warrant major action, but simply awareness and future monitoring.  However, all of them put together, and in a public setting such as this, constitutes a major hazard in my opinion.

So the next time you are out in your yard, simply look at your trees.  If you see any of these warning signs, consult a certified arborist.  Maybe nothing needs to be done except future monitoring.  But take it from me, a large tree on top of your house is nothing you want to happen.  Replacing a hazard tree with a new tree is not the worst thing that can ever happen.

Jay

www.rvascapes.com