How To Spot a Dangerous Tree

This article is reprinted with permission of the author, Peter "Treeman" Jenkins, ISA-Certified Arborist -- © TreeInspection.com, 2010

Every year, falling trees or branches cause tragic deaths and tens of millions of dollars in property damage. As a result, some homeowners have come to the unfortunate conclusion that they should get their big trees removed. But if the tree is healthy, this isn’t necessarily the best course of action!

Most homeowners value their trees. They have tried not to be intimidated by tree accidents or scared by unscrupulous tree companies trying to score a job. However, most people do want to protect themselves. The problem is, they often don’t know what to do for their trees or who or where to turn for help.

This article will detail how homeowners with little or no knowledge of trees can examine the trees in their yard themselves in order to safeguard against the most common problems presented by urban trees.  We teach this not to deter people from calling a professional, but rather to add to the safety of your home and family by monitoring your trees yourself for potential dangers. The homeowner’s tree inspection does not eliminate the necessity of hiring a Certified Arborist periodically to come out and make sure you haven’t missed anything. There is no substitute for hiring a professional—a Certified Arborist, whose experienced and trained eyes can spot problems not always visible to others.

What is a Certified Arborist?

An arborist is someone who takes care of trees. He might work for a tree service, a public utility, a government office, or any other employer whose work involves trees in some way. A Certified Arborist is someone who has extensive education and field training, and has passed a qualifying exam given by the International Society of Arboriculture (ISA). The ISA is a large non-governmental membership organization which sets professional guidelines for the arborist; it also offers a broad variety of educational programs and resources to its members and the public around the world. Since there is no license required by most states (including Georgia) to perform tree work, the ISA certification tells you that you’re working with someone who (usually) knows what they’re doing.

The Tree Inspection

Warning! Homeowners need to know that living under a large tree poses a certain element of risk. The tree might be perfectly healthy and end up on your house or worse as a result of weather events like straight line winds (a gust of wind usually associated with thunder storms), ice storms, excessive rainfall causing saturated soil, or a number of other natural variables. There are a number of things you can do to help keep your trees around, but be aware that trees are not 100 percent predictable.

Trees which are hazardous often present signs and symptoms that any person armed with a little bit of knowledge can see. Once you understand what the tree is showing you, you’ll be in a better position to decide whether you should hire a Certified Arborist for a full evaluation and advice.
It’s a good idea to inspect your trees personally after every season change. It’s even more important to take a look at your trees after a heavy wind storm or after many days of heavy rain. If you find any of the conditions described below, call a Certified Arborist for verification, diagnosis, and treatment. The treatment might range from getting a few branches cut or taking out the entire. Don’t wait for the tree to drop large branches, get sick beyond the point of recovery, or topple before you take action! This is especially true if the tree is located over your house, parking area, or in areas where you or others like to hang out.

Inspect the Four “Zones” of a Tree

A thorough tree inspection should include a check of the four “zones” of the tree: a) an overall view of the entire tree, b) the ground around its base, including the roots, c) the trunk, and d) its canopy of branches and leaves.

  1. The Overall Tree. Most people look at trees without really noticing them. To someone who is not very observant, all trees look pretty much the same. But when you know what you’re looking for, you realize there are a great many differences from one tree to the next.
    >From a place where you can see the entire tree at one time, focus on the tree alone and really look. Is it leaning? What is it leaning toward? If you think it’s always had a lean? Is it leaning more than it was a week or month ago? Can you see any big dead branches? Is the tree’s leaf cover thin, or are there some leaves that are dropping much earlier than the rest? Are there sections of the tree where there are no leaves at all? If the answer to any of these questions is “yes,” you should call a Certified Arborist. You may have a tree that’s sick or in the process of dying or falling over. It may not matter that the tree is unhealthy if it is in a wooded part of your backyard with nothing that will get damaged when it falls. Or, if the tree is generally healthy, it may just be shedding some limbs it doesn’t need any more. But if the tree is over a play area, an area where people walk frequently, or near enough to the house to make the house a target if it falls, you should get it evaluated. Better to be safe than sorry.
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  3. Ground Inspection. A tree is held up and fed by its root system. There are two types of tree roots. The anchoring or structural roots support the tree; these are the most visible. The absorbing roots are much greater in number and are not seen. They provide the tree with water and nutrients from the soil.

    When the anchoring roots rot and decay, the tree is in trouble. The tree can fall at any time. A tree can appear healthy and vibrant with foliage but suddenly fall over if the structural roots are not strong enough to keep it standing. Don’t wind up regretting that you didn’t look at the ground around a tree which appears healthy and fully clad with foliage. If there are serious structural root problems, the tree is dangerous. Even if the tree is standing completely straight, a gentle wind or rainwater sitting on its leaves could cause it to topple without warning. 

    The ground and soil surrounding the base of the tree can provide clues to a serious root problem. Pull back any ivy or ground cover to get a good look at where the soil meets the trunk. You might see cracked or raised soil, which may indicate root disturbances and a tree in the process of uprooting. Fungal growth, such as mushrooms, on or near the tree’s roots or trunk is indicative of rot and decay. The presence of fungus is particularly serious if it is profuse, because fungus grows only on decayed wood. To determine if the tree is unsafe, that is, if it has enough strength to hold itself upright, you need to know how extensive the decay is. Call a Certified Arborist to help you make a decision about your tree.

    Are there dead branches on the ground? If you see dead branches on the ground that have fallen out of the tree, chances are good there will be more up in the tree. This is especially true if your tree has never been cleaned out by a tree care professional. The trained eye of a Certified Arborist can often spot dead branches you might not see yourself.

    Finally, look for coarse or fine sawdust (also called "frass”) at the base of a tree. If it’s there, your tree has probably been attacked by insects. A borer invasion (small beetles) is usually fatal to a tree, but depending upon the tree’s species, it may be possible to save the tree if the bug invasion is caught early. In this case, call a Certified Arborist with experience applying pesticides. In Georgia these professionals must have a license. Don’t be shy-- ask for a copy! Make sure you are working with someone who is reputable.
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  5. Trunk Inspection. The trunk is what holds up the tree. It supports the massive weight of the branches. You are in big trouble if the trunk fails and all of the branches come down with it.

    Inspect the trunk thoroughly to help you identify weaknesses or disease. If there are cracks or cavities in the trunk, the entire tree can break or split. The presence of a cavity does not necessarily mean that the tree needs to be removed. Factors to consider include how extensive the cavity is, where the cavity is located, where the tree is growing, and the overall state of the tree's health. This is where you need the trained eye of a Certified Arborist.

    Look for places on the tree’s trunk where there is no bark or the bark is falling off. This can indicate a dead section or a fungus attack. A long streak of missing bark coming down the tree usually means the tree was struck by lightning. Some trees survive a lightning strike; you’ll need to take another look about six or eight weeks later to see whether the tree is losing its leaves.

    Insects often attack a sick tree’s trunk, leaving very fine sawdust shavings that are clearly visible because they are light in color. Ants boring into decayed wood leave coarse shavings. Pine bark beetles attacking a pine tree leave “pitch tubes” that resemble marble-sized balls of light colored sap. They look like popcorn stuck on the tree.

    If any of these conditions are present, call a Certified Arborist immediately to decide if your tree is stable enough to preserve or whether it should be removed.

    Multi-Stemmed Trees Trunks. Sometimes a tree grows two or more trunks. The points where the multiple trunks connect must be inspected for weakness or past storm damage. These leaning trunks sometimes crack and split where they connect or grow layers of bark (“included bark”) instead of strong wood. Stronger connections appear as a “U” shape at the junction; a tight “V” shape usually indicates a weaker connection. To prevent a double-trunk tree from splitting apart during high winds, a cable might be installed high in the tree to provide mechanical support. Multiple trunk trees should be inspected by a Certified Arborist.
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  7. Canopy Inspection. One of the most common and obvious tree dangers is dead wood. Trees naturally shed dead branches if they are not getting any sunlight. You can spot dead wood easily: dead branches don’t have leaves. A dead pine branch will have brown needles if they died recently. If branches have been dead for a longer period of time, the bark will fall off. Also look for broken branches, especially after a strong storm. You might not even know a branch is broken after a recent storm until a month later, when the leaves turn brown. Pockets of decay or rot sometimes exist on the upper side of a branch, where they are invisible to a ground observer. This is where an aerial tree inspection by a Certified Arborist can be very helpful.

    To protect yourself, your home, and the health of your tree, have weak, broken, cracked, or dead branches removed.

General Tips

To get the best care for your tree, hire a Certified Arborist. Certified Arborists have an understanding of a tree's needs and an eye for potential hazards. Unlike others who may want to profit from your lack of knowledge about trees and their care, most Certified Arborists will do their best to protect and preserve your trees. Generally they will not recommend removal unless it is necessary.

  1. If you are having work done on live trees, do not permit climbers to use leg spikes to climb into the canopy. Leg spikes injure, disfigure, and sometimes kill trees.

     


    Expect to pay a fee for a tree inspection. You are paying for an arborist's knowledge, years of experience, and time. A “free” tree inspection sometimes fetches unnecessary tree work, for the sole benefit of the tree company. Not many tree companies will send out an inspector without the expecta¬tion of landing some kind of work. Try to get an unbiased opinion.
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  3. The cheapest estimate may not always be the best deal!  A “bargain” estimate can signal many problems: the bidder is not qualified to perform the work; the bidder’s work is so bad that he has trouble getting better paid jobs, or possibly the company pays extremely low wages.

    There is usually a tradeoff between the job that’s done too quickly, sloppily, and cheaply by a fly-by-night company, and the work that’s done carefully and safely at a reasonable price by a reputable company. Improperly pruned trees can never recover. Be careful who you hire!
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  5. Don’t be afraid to ask questions. If a tree inspector declares that a tree needs to be removed, ask how he came to that conclusion. If he says something vague, along the lines of “this tree might fall down,” and offers no supporting evidence, don’t take his advice as “the truth.” Many trees are removed unneces¬sarily because the inspector wanted to make a sale. If he appears unreliable or untrained, get another opinion! Keep your trees if you can. Trees are valuable, not only for environmental purposes but property value as well.

Be proactive. Check out your trees. If you see something suspicious, call a Certified Arborist. If your tree does not look healthy, call in a professional to take a look. If you feel uneasy or are losing sleep over a tree, make that call. Don’t let Mother Nature take care of a problem before you do!