Recognizing When Trees Become Hazardous

A tree that topples at the wrong time or in the wrong place can cause significant damage to your home and property. Worse yet is the possibility that it could injure or kill someone. Here are some guidelines to help you recognize whether or not a tree has become a hazard, and as well as some steps you can take to correct the situation.

What is A "Hazard" Tree

The U.S. Forest Service defines a "hazard tree" as one with structural defects that are likely to cause the failure of all or part of the tree, which could result in striking a "target." A target can be a vehicle, building, or a place where people gather such as a park bench, picnic table, street, or backyard.

The Most Likely Candidates

Certain trees are more likely to become hazardous due to any number of contributing factors:

• Age: Older trees have been exposed to environmental factors for many years and may become hazardous due to the accumulated effects of age. Young trees are susceptible, too. Aspen, for example, are known to be prone to breakage when they are young due to decay and disease. Tall trees are susceptible to lightning strikes, which can jump to nearby buildings.
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• Species: Some tree species are more susceptible to injuries. For example, splits can occur on the trunk of the tree as well as on branches. Trees which are most susceptible to this type of injury are those which are thin-barked, such as certain fruit trees. Maple and ash are prone to weak branch unions, while birch tend to "self-prune" as they decay, eventually leaving only a hollow trunk.

• Location: Trees bordering wooded areas, roads, driveways, and parking lots, risk greater exposure to storms and other environmental stressors. Trees near construction zones may suffer root damage during land clearing. Those growing in saturated or shallow ground are more susceptible to toppling due to the ground giving way.

Assessing the Risks

An annual visual inspection of your trees is a good way to spot potential problems. A pair of binoculars can help you assess the hard-to-see upper branches of tall trees. A tree with defects only becomes hazardous when it has the potential to hit a target. Keep in mind though, that not all defects are structural. A tree appearing structurally sound can still be a hazard if it obstructs the view of a passing motorist, causes a sidewalk to buckle, or interferes with nearby power lines.

When performing your inspection, ask yourself the following questions:

• Does the tree appear healthy? Does it still produce needles or leaves?

• Has the tree lost large branches recently? Are any of the remaining branches dead?

• Are wide (or deep) cracks visible in the trunk, branches, or branch unions?

• Is the tree producing heavy new growth around topping cuts?

• Are there broken branches dangling from the tree?

• Are branches close to interfering with power lines or windows?

• Are the roots causing damage to a nearby foundation?

• Are fungus (mushrooms) growing on the tree's roots?

• Are hollows or cankers (dead spots) visible on the trunk?

• Is the tree leaning? If the tree falls, could it hit a car, house, utility line, or person?

• Have the roots, trunk, or branches been recently injured by storms or construction?

Investigate Your Options

If you answered yes to one or more of the above questions, you may want to have the tree evaluated by a certified arborist or tree professional and give you recommendations on corrective action. Before deciding what action to take, investigate your options.

• Relocating the target. It's a cheap and easy solution, but one that's often overlooked. If target objects like swing sets, cars, and picnic tables can be physically relocated, your problem is solved.

• Corrective pruning. You may be able to remove dead or damaged roots and/or branches through pruning without having to disturb the rest of the tree.

• Removal. If over 30 to 50 percent of the main branches or trunk are severely split, broken, or mutilated, the benefit of extensive repairs is probably questionable. This is usually a job best left to the professionals.

Hiring a Good Tree Service

When getting estimates for work, look for companies that employ certified arborists. Make sure they carry the proper state certification and licenses and that they are fully insured. You can find one near you by visiting http://www.treesaregood.com and typing in your zip code.

Trees don't live forever, but removing the hazard doesn't always mean removing the tree. Always consider the risk as well as the long-term consequences. Then try to create a landscape plan that allows for the perpetual cycle of planting, maintaining and replacing trees.