If a tree has a cavity or hollow and is near a building or area used by people, have it checked by a competent arborist. This is likely to spread decay to healthy living portions of the tree. Do not drill holes in the bottom of the cavity to remove water. Do not attempt to clean out the inside of the cavity or hollow. This should not injure the tree as long as the walls of the cavity are not injured during the repair process. Spray insulation has been used to keep animals and children out of cavities. Never use concrete in trees.Ĭavities do not have to be filled. This abrasion allows decay to move into the living wood by injuring the barrier zone formed by the tree to retard the further advance of decay. The additional injury occurs when the tree continues to move normally in the wind against the stiff concrete column inside. We now know that this actually causes more injury to the tree. In the old days, cavities were filled with concrete in hopes that this would strengthen the trunk. Injuries could include removing a branch with a pruning cut made too close to the trunk, removing a large branch, large branch breakage, topping the trunk or branches, cutting a large root or a group of roots (see right photo), or damaging the trunk. The injury often occurred many years ago (see photo). “Cavities and hollows in trunks and branches are typically the results of decay that followed injury. Here is a great explanation published by the University of Florida Extension Agent There is no consensus among arborists that standing water will increase the hollowing of the tree.
I guess it could be argued that standing water could also attract fungi or pests as well. The other idea that comes up is drilling a hole to let the water leak out but again this has a way of creating a hole that pests can enter or promote further decay in the surrounding wood. In this case, putting soil in the cavity might just make it a breeding ground for pests that can invade the hole. Why? Our commercially available cavity fillers haven’t been shown to improve tree health and outcomes. Can I fill this in with soil and cause no problems? Should I fill it with something else- foam? Should I leave alone?Īnswer: We get a lot of variations of the above question and typically the best way to handle this is to do nothing unless you can find an elegant way to divert the water. The real question: My mom has an old oak that has developed a cavity between two roots that is hollowed out into the tree and is holding water.