Choosing a Safe Tree

A Climber's Guide to Tree Inspection

by Peter “Treeman” Jenkins, Founder of TCI and ISA-Certified Arborist

There trunk bulge--smThis tree looks friendly, but is it?are many risks in trees that can be seen if you take the time to look and are aware of what you're looking for. Some hazards are obvious to the naked eye, such as a severe lightning strike or dead leaves during the summer. Some hazards present themselves as clues needing further investigation. Others can be seen only upon close inspection.

Always check a tree for its health and for potential hazards before you climb it. It doesn’t matter if you have climbed the tree many times before. Conditions change! Branches can die or partially break from a storm the night before; a tree can partially uproot after a wind event. Any tree's condition can change very quickly.

Train yourself to look with a keen eye. Always inspect your regular climbing trees in the springtime when the trees have produced new leaves. Are there any new dead branches? Also, check your trees for broken branches or a lightning strike after a severe storm.

There are four distinct assessment “zones” to look at before you climb a tree. What follows is a discussion of each to determine how and what to look for to detect potential risks in a tree.


  • Zone 1: The Wide Angle View

    Crack in major leaderCracked branchLook at the tree from a distance to get a feel for it as a whole. A tree’s lean will often be more evident seen from afar. Branches that are broken or split might be more readily seen, such as the crack in a major branch (leader) at right. Sometimes branch angles will look out of place or unusual. Power lines are often seen more clearly from a distance. Don't go near a tree such as this one if you see obvious signs of danger.

  • Zone 2: The ground around the base and three feet up the trunk

    The ground zone includes the area around the base of the tree and three feet up the trunk. This includes the ground close to the trunk, the tree’s base, and its root flares. Watch your step! You may not think it is dangerous to walk up to a tree until you step on a yellow jackets’ nest in the ground, twist an ankle on a hidden hole, or walk through poison ivy. Pay attention to where you are putting your feet! Don’t get a case of “tree hypnosis” as you walk toward the tree. Stop walking when you look up.

    • Raised soil

      Uprooting tree

    • Deadly fungus

      A bad case of Ganoderma
      at the tree's base

    • Cavity

      This cavity doesn't look
      very deep, but it is!

    The ground zone can provide valuable clues to serious tree problems. Raised or cracked soil, especially on the side opposite a tree’s lean, can indicate a tree in the process of uprooting. If the tree is leaning, look behind the trunk’s lean for signs of upward heaving in the ground or air spaces between the ground and trunk. Sometimes putting your head close to the ground for an “ant’s eye view” can give you a clearer perspective of ground swellings or roots heaving upwards.

    Be wary if you see dead branches lying on the ground. It’s a good bet there will be more of them up in the tree. Step away from the tree and look up again. Use binoculars from a safe distance to get a closer look.

    A tree is supported and held up by its root system. There are two types of roots. The supporting (or anchoring) roots are the most visible. They hold a tree in the ground, and serve as storage containers for sugars produced through photosynthesis. The absorbing roots are tiny root hairs that can exceed thousands of miles if the lengths were added together. Their function is to pull water and nutrients from the soil.

    The presence of fungus on or near a tree trunk points to root decay and trunk rot. Stay away from a tree if you see profuse fungal (mushrooms-like) growth around the root flares or trunk of the tree. Fungus indicates decayed wood, and can be particularly serious if it is profuse, depending on the species of fungus. While the anchoring roots may be decayed and rotten, the tree can still appear healthy and fully clad with foliage because the tiny absorbing roots are still actively supplying the tree. However, if the anchoring roots that hold up the tree are no longer providing support, a gentle wind or even rainwater sitting on the leaves can cause the entire tree to topple without warning.

    Look at the base of the tree and up three feet (1 meter). Do you see a cavity? A tree with a cavity has lost strength. Use a stick to probe a cavity opening to get an idea of how deep it is. (Never stick your hand into a cavity because wild animals often live there and you could get bitten.) Larger cavities signal a larger strength loss. Tall trees with cavities are more dangerous than shorter trees with cavities because wind places an increased leverage factor. A tree is much more dangerous if there is more than one cavity opening at its base. However, the presence of a cavity does not always mean the tree is unsafe. The amount of risk depends on how extensive the cavity is, where the tree is growing, and the general overall condition of the tree.

    Unusual bulges indicate a tree is trying to compensate for a loss of strength by adding layers of growth. Cracks and splits in the trunk are more serious and point to the possibility of the tree breaking.

  • Zone 3: The trunk

    The trunk (or stem) of the tree is the main supporting structure that holds up the branches.

    Sometimes an excessive trunk lean can cause a tree to fall. See the section “Leaning Trees” to learn more about leans. 

    Absence of bark on the trunk can indicate a dead section or a fungus attack. Large areas of the trunk that do not have bark indicate a larger section of dead wood and thus increased risk of tree failure.

    A long streak of missing bark coming down the trunk usually means lightning has hit the tree. Use binoculars to look into the treetop for cracked, shattered and/or broken branches.

    • Lightning strike

      Lightning strike on pine tree

    • Borer Frass

      Borer frass

    • Pitch tubes

      Pitch tubes on pine trunk

    • Weak trunk connection

      Weak trunk connection

    If insects attack a tree’s trunk, you will probably see frass, the fine light-colored sawdust shavings like the borer frass at left. In pine trees, the presence of “pitch tubes” resembling little balls of light colored sap about the size of a marble is a sign of beetle attack. Expect to see dead branches in the crown (if not an entire dead top) if insects are present, because they or their larvae often block the flow of water to the treetop.

    In double- or triple-trunk trees, the points where the multiple trunks connect must be inspected for weakness or storm damage. Weak connections are usually evidenced by a tight “V” shape, similar to the junction here. Look closely to see if there are any visible cracks in this area. Sometimes you’ll see an unusual ridge of wood growing down from the intersecting V connection, usually on both sides. This is a sign of an old crack under the surface or the tree’s effort to strengthen the weak area. It’s best not to climb in trees with these formations because they are more prone to splitting, and they will snag your throwlines. If you do climb trees with these formations, climb on the sections that are more vertical and avoid sections that lean outward. Watch for branches that have these weak connections, as they, too, are prone to breakage.

  • Zone 4: The Crown

    Almost every large tree has dead branches. However, the location and amount of dead wood in a tree can tell you much about its health. Dead branches in the lower sections of a tree are normal and usually a sign of inadequate sunlight. The tree will naturally shed these. Branches dying back from the tips indicate that the tree’s health is somehow compromised, though dead twigs might be too small to cause any threat to a climber. A large number of dead branches high in the treetop usually means the tree is dying. Brown leaves or the absence of leaves (with the rest of the tree in full leaf) indicate a dead branch. The loss of bark and/or fungus growing on a branch also indicate a dying or dead branch.

    The broken branchmost obvious way to prevent risk in a tree is to remove dead or broken branches. Dead branches can be easily spotted when the tree is in full leaf. Use binoculars for a closer look as you look for broken branches. Pruning a small amount of annoying twigs that get in your way does not harm a tree.

    Decay or rot pockets sometimes exist on the upper side of a branch, making them invisible to ground observation. To avoid accidental branch breakage, it’s better to climb a tree close to the trunk (trunk route) if it is a wild or unfamiliar tree, rather than climbing out on branches (branch route). The weak branches need to be pruned or avoided in future climbs.

    "Widow makers" are life-threatening broken branches that are hanging precariously or lodged in a tree. These branches can come crashing down with a slight wind or be shaken down or dislodged by a gentle touch by a climber in the tree. Climbers of wild trees must be constantly aware of dangerous broken branches, which should be identified and avoided.

    IMPORTANT! Dead branches and widow makers should be removed by the lead climber before the rest of the climbing party enters the tree. When widow makers or dead branches are being removed, it is particularly important that the lead climber, as well as those who might be even remotely near the tree on the ground, wear a helmet.

  • Leaning Trees

    leaning tree

    A tree with a lean may present particular challenges and benefits to a climber. Trees leaning out over water or hillsides can offer a beautiful view of the surrounding area. However, climbing dangers include the possibility of the tree uprooting or breaking under the added weight of a climber. Check for the following before climbing a leaning tree.

    • The trunk base opposite the tree lean. Rake back the leaves around the trunk on the opposite side of the lean. Look for air spaces between the dirt and the trunk, which can signal a tree in the process of uprooting. Fungus or decayed roots opposite the lean increase risk significantly.
    • Raised soil. Inspect the ground for raised or cracked soil opposite the lean and/or broken root ends emerging from the soil. These signal a tree in an advanced stage of uprooting.
    • Cracked trunk. Leaning trees often show visible cracks produced by the tremendous weight stress. Carefully look around the first ten feet (3 meters) of the trunk. The cracks are usually obvious because of the exposed lighter colored sapwood or raised seam ridges over older cracks.
  • Dead Trees

    Recreational climbers should never climb a dead tree. Dead trees can topple at any time. Don't even walk under them, as they can shed branches or fall apart at any time. It's not hard to distinguish a live tree from a dead tree when foliage is present. However, during the winter months the difference is not so obvious. Here are some clues which indicate a tree which is dead or dying:

    • Dead branches on the ground. Wind and rain will naturally break off dead branches. If you spot some dead branches lying on the ground, especially large ones, step out from under the tree and look up. Try to locate where they came from. You can usually see where they have broken off. If you see numer­ous broken branch ends above you, consider the tree dangerous and unsafe. Needless to say, if you see a tree with few branches left attached to it, it has been dead for a considerable length of time.
    • Missing bark. When a tree dies, sections of bark will drop off. Sometimes a branch or only a part of the tree will die, and the bark will eventually drop off the dead section. If you see that a tree is totally devoid of bark, the tree has probably been dead for a while. Softwoods, such as pines, will lose their bark more quickly than hardwoods, and are much more unpredictable. Move away from the tree immediately!
    • Discolored bark. Obvious areas of discoloration, like blotches of gray, can often mean fungus attack. Don't get discoloration confused with lichen or moss growth, which is natural in humid regions.
    • Absent buds. Look at the tips of branches with binoculars. If they don't have buds or they appear stunted, the tree or branch may have recently died. It may be helpful to compare the bud ends with trees of the same species living in the immediate area.
    • Fungus growth. Tell-tale fungus grows only on dead and decaying wood. If it’s found on the ground, there is usually root decay. Fungus growth on a tree trunk signals dead or decayed wood. Branches with dead or decaying sections can also harbor fungus growth.
    • The presence of leaves in the middle of winter. If you see brown leaves on a hardwood tree in the middle of winter and there are no other trees of this species with this sign, consider this tree dead. It died the previous season and the normal process of leaf fall (abscission) did not occur. Move away from the tree immediately. (One exception to this rule is the American beech, whose brown leaves in winter add lovely color to the treescape. This tree sheds its dead leaves in the Spring.)
  • Poison Ivy: "Leaves of three, let them be!"

    Poison ivy can occur as a ground cover or as a creeping vine on a tree. It is charac­ter­ized by its compound leaf structure, divided into three leaflets. The vine stem clings closely to the tree and is covered with fine, reddish brown fibrous root hairs that appear furry as compared to other vines. The separate twigs that support the leaves often grow straight out from the trunk of the tree in a ninety degree angle up to three feet (1 meter). In the Spring, poison ivy bears white, berry-like fruits which are eaten by birds but are poisonous to humans. The leaves turn a bright red color in the fall before falling off. All parts of the poison ivy plant contain a volatile resin that can cause severe skin inflammation, itching and blistering. People who are hyperallergic to poison ivy react violently, necessitating an immediate visit to the emergency room to prevent asphyxiation.

    • Mature poison ivy

      Eastern poison ivy (mature)

    • Young poison ivy leaves

      Young poison ivy leaves

    • Poison ivy vine--note the fine red hairs

      Poison ivy vine--
      note the fine red hairs

    • Western Poison Oak

      Western (or Pacific) poison oak

    Take precautions if you suspect there is poison ivy in the area. Put your gear on a ground tarp when you take it out. Use a rope bag during your ascent and descent to prevent rope contact with the poison ivy. Some sensitive climbers get good results from coating their skin with preventative salves prior to a climb.

    If you suspect exposure, do not try to wash off poison ivy with hot water! The heat opens your skin pores and may aggravate more than help the situation. Instead, wash thoroughly using cold water as soon as possible. If you wipe yourself with rubbing alcohol or other specialized solutions which act as a solvent to remove the irritating resins (such as tecnu), the effects of poison ivy can often be avoided. Don't leave home without it!

    Important: Before you venture out, always ask your climbing team if anyone is especially allergic to poison ivy. You will choose a climbing tree that has no visible poison ivy. To be safe, your partner should prepare by wearing a long-sleeved shirt, gloves, and take other preventive measures.

    Finally, don't spread the toxic poison ivy resin through its exposure to infected articles like clothing, shoes, and climbing rope. Wash all ropes that have been exposed to poison ivy. Use a mild detergent that does not contain bleach. You could save yourself or others who may use your rope months later from a severe reaction.

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