If you need to identify hazardous trees in your landscape you should contact an experienced arborist. An experienced arborist or even an ISA Certified Arborist has the skills necessary to know what conditions lead to trees becoming hazardous trees. So, what does an arborist look for when inspecting a tree to determine if it is a hazardous tree?
Cavities in a tree trunk or in large limbs are an obvious cause for concern. Cavities weaken the structural integrity of the tree. The width, height, and depth of the cavity in relation to the tree trunk or limb determines how much structural weakness has occurred.
Cracks in a tree trunk or cracks in larger tree limbs are easy to see and will raise a red flag for the arborist inspecting the tree. The orientation of cracks in a tree is also important. Vertical cracks in a tree trunk are a sign of structural damage in a tree, but horizontal cracks in a tree trunk are a sign of even more advanced structural weakness. An arborist should be consulted anytime you see cracks in one of your landscape trees.
Sometimes structural weakness in a tree won’t cause cracks, but abnormal seams will develop on the surface of the tree trunk. The casual observer may not notice seams developing which is why it is important to consult with an experienced arborist.
Creaking or cracking noises emanating from the tree could indicate there is a crack in a limb, the tree trunk, or be caused from rubbing branches. Any of these causes of noises coming from your tree is a reason to have an experienced arborist inspect the tree and for corrective action to be taken.
An experienced arborist will try to determine if there is internal decay in a tree. There are several methods that can be used to check for internal decay in a tree. Tapping the tree trunk with a rubber mallet, know as sounding, has been used for decades to check for internal decay in a tree. More recently, drilling with a small diameter drill bit has been used to check for internal decay in a tree. Wood resistance and color can indicate if internal decay is present. A more advanced drilling tool called a resistograph uses a very small diameter drill bit and displays wood resistance in a graphical format. If internal decay in a tree is found an arborist can apply certain mathematical formulas to determine a range of risk associated with the structural weakness caused by the decay.
Internal decay in a tree trunk sometimes causes abnormal bulges to develop on the tree trunk. Abnormal tree trunk bulges may develop on a small section of the tree trunk or the whole circumference of the tree trunk.
Leaning trees may grow for years or decades without causing concern, but a change in the lean of a tree is a sign of trouble. If a change in the lean of a tree is noticed the soil around the tree needs to be inspected. Lifting of soil around the base of a leaning tree is a time for immediate corrective to be taken. In some cases there is no lifting of soil around the base of the tree, but cracks in the soil start to develop. In either case an experienced arborist should be contacted to inspect the tree.
Fungal growths on a tree trunk or mushrooms growing under a tree may be a sign of advanced decay in the tree trunk or on the tree roots. Fungal growth on a tree trunk is almost always a sign of internal decay in a tree trunk. Mushrooms growing under a tree are not necessarily related to tree root decay. This is where an experienced arborist can be an invaluable resource when determining if a tree is a hazardous tree.
These are not the only conditions an experienced arborist will use to determine if a tree is a hazardous tree. The location of the tree, what kind of care the tree has received in the past, and construction activities around the tree are some of the other factors an experience arborist will take into account when determining if a tree could be considered a hazardous tree. What is most important is to not delay in contacting an experienced arborist if there is any question as to the safety of one of your landscape trees.