Hazardous trees pose a danger to people and property. When storms or high winds hit, limbs – and often whole trees – fall to the ground.
“Many fatal accidents and millions in property damage can be averted if homeowners heed the warning signs of a hazardous tree,” explains Robert Rouse, staff arborist for the Tree Care Industry Association. “By not paying attention to your trees, you are placing your property, even your life, in potential jeopardy.”
Tree Defect Clues
Fortunately, one can often read the clues which indicate that a tree is prone to failure. For instance, if a tree has large branches attached with tight, V-shaped forks, you should consider having those branches removed or lightened. Other warning signs of structural instability include cracks in the trunk or major limbs, hollow and decayed areas, or the presence of extensive dead wood. Mushrooms growing from the base of the tree or under its canopy may be a sign of root decay. On the other hand, just because you may not see fungus growth does not mean there is no decay.
“It pays to be highly suspicious of any tree that has had construction activities – such as trenching, addition or removal of soil, digging or heavy equipment movement – anywhere under the spread of its branches,” says Rouse. These activities can cause root death, which in turn could lead to the structural instability of the tree.
The sign most people recognize is a hollow in a tree. But even a large hollow does not necessarily signify a tree has become hazardous. Nor does it mean the hollow should be filled. Filling of hollow trees, a process called “cavity filling,” was practiced by arborist for many years. However, thanks to modern research, it has been discovered that cavity filling is not needed to support or improve the health of hollow trees.
Tree experts found that cavity filling with cement can actually damage a tree. According to Rouse, “the column of cement created in the tree by a cavity fill doesn’t move, just like a column on a building, but the tree is always moving. It sways with the wind constantly. The rubbing created by the swaying tree and the solid column of cement further damages the tree.”
Wood decay fungi that created the hollow in the first place are able to take advantage of the new injuries created by the rubbing and invade the remaining healthy tissue of the tree. If cavity filling is desired for aesthetic reasons, there are some new synthetic foams that can be sprayed into the cavity by professional arborists. These materials will bend with the swaying tree, reducing injury. However, there is really no reason to fill a cavity other than for aesthetic reasons; it doesn’t improve the tree’s health and doesn’t offer any added support. If structural support of a tree is required, a professional arborist will recommend cables, braces, tree guys, or removing the tree, not cavity filling.
Homeowners should consult a professional arborist before storms arrive. Contact the Tree Care Industry Association (TCIA), a 65-year-old public and professional resource on trees and arboriculture. It has more than 2,300 member companies who recognize stringent safety and performance standards, and are required to carry liability insurance. An easy way to find a tree care service provider in your area is to use the “Locate Your Local TCIA Member Companies” program. You can use this service by calling 1-800-733-2622 or by doing a ZIP code search on the TCIA Web site, www.treecareindustry.org.