If you notice that one of your trees has large hollows in its trunk, you might assume that the tree has died, and needs to be removed. The reality is more complicated; while some hollow trees will need to be felled for safety reasons, others will remain completely healthy and stable and can live for decades. If you have one or more trees on your property with hollow trunks, figuring out whether to remove them or keep them can be difficult.
Why Do Tree Trunks Become Hollow?
It may surprise you to learn that, in most cases, most of a tree's trunk is made of dead wood. Only the sapwood, a relatively thin layer of wood around the edge of the trunk, is alive and growing.
The inner bulk of the trunk is composed of heartwood, which is not living wood and does not contain any sap or water. Because the core of a tree's trunk is dead wood, it is not protected by the tree's immune system and is more vulnerable to fungal rot and infections.
If fungus reaches a tree's heartwood, it can consume the heartwood quite rapidly, destroying the trunk from the inside out. This rot usually stops once the fungus reaches the outer layer of sapwood, which can effectively fight off the infection. If a tree's heartwood has been partially or completely consumed by fungus, but the sapwood stays unaffected, the trunk will become hollow.
Should Trees With Hollow Trunks Be Removed?
Large hollows in a tree's trunk can look quite dramatic, but in many cases, the remaining, living portions of the tree remain completely healthy. As heartwood is broken down by fungus, it releases minerals and other nutrients into the soil, so heartwood rot and hollowing can actually benefit a tree's overall health. Hollows in tree trunks also provide valuable shelter for many animal species, such as owls and woodpeckers.
However, a tree's heartwood also provides the tree with more weight and bulk, improving its wind resistance. Some trees with hollow trunks may topple during high winds, posing a serious risk to nearby structures (not to mention people). As a general rule, hollow trees with thin layers of sapwood are more vulnerable to toppling than those with thicker sapwood.
It is also worth mentioning that a small number of tree species have trunks that only contain sapwood, with no heartwood. If one of these species has a hollow trunk, it is almost certainly diseased and dying, and will need to be removed as soon as possible.
To determine whether your hollow-trunked tree needs to be removed, you should call in a professional tree removal company as soon as possible. These tree experts will examine your tree's overall health, test its structural stability, and determine whether the tree is safe or needs to be removed.