Trees get cavities too. Find out how to evaluate the health of a holey tree.
It’s very common for trees to develop holes in limbs or trunks as the grow and age. Arborists generally refer to these as cavities or pockets of decay.
They can be started by a variety of factors — both man-made, such as poor pruning techniques, and natural, like the loss of a large limb during a storm. Any damage to the bark and outer tissues of the tree can potentially start the process that leads to a cavity or hole down the road.
A healthy tree is generally able to deal with wounds or cuts that may arise by building a series of walls within its wood (Google the acronym CODIT and Dr. Alex Shigo for more information on these walls).
If one or more of these walls fails, it becomes a pathway for decay-causing organisms to make their way inside the tree. This begins the process of breaking down wood within the tree that can ultimately lead to a cavity years or decades down the road.
Don't chop that tree down yet
Not every tree with a cavity needs to be removed. Cavities are part of outside life for a tree, and as a result they’ve developed strategies to try and compensate for these issues.
Building walls within their tissues to help prevent further spread of the decay and enlargement of the cavities is one defense mechanism trees have evolved.
Another is growing additional amounts of wood in the areas where decay is the greatest to try and compensate for any strength loss. Both of these reactions are best exercised in healthy trees.
Trees that are under stress or in declining health may not be able to devote the resources needed to perform these protective actions.
Ask an arborist to evaluate your trees
So, what can you do if you have a tree with a hole or cavity? As always, have an arborist inspect the tree and evaluate the cavity.
There are a good number of factors to consider when looking at a tree and an area of decay. The age, species, wind exposure, past history, and placement of the cavity are just a few factors an arborist will consider.
Filling cavities or holes with concrete or foam used to be pretty common in the industry, but both have fallen out of favor. There may be some specific instances where covering the hole might be recommended, but filling it really won’t do anyone — including the tree — any good. There’s a decent chance that by sealing off the hole from the outside, you can be sealing in pathogens and organisms that won’t be beneficial to the tree.
One final word of advice about holes in trees: Please do not just reach your hand into one! A whole variety of animals love to live in trees and might be spooked by you reaching in through their front door.
Do you own any trees with holes? Tell us about your experience in the comments section below.
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