A Climber's Guide to Tree Inspection
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. Look behind the trunk’s lean for signs of upward heaving in the ground or air spaces between the ground and trunk. (See “Leaning Trees” below for more information.)
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.
If insects attack a tree’s trunk, you will probably see frass, fine light-colored sawdust shavings like the borer frass (left). In pine trees, the presence of “pitch tubes” resembling little balls of light colored sap about the size of a marble (right) 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 obstruct 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 (included bark) 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 (seam) of wood growing down from the intersecting V connection, usually on both sides. This is a sign of an old crack under the surface (repair seam) 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
The location and amount of dead wood in a tree can tell you much about its health, and almost every large tree has dead branches. Dead branches in the lower sections of a tree are normal and a sign of inadequate sunlight. The tree will naturally shed these. Branches dying back from the tips like on the tree at right indicate that the tree’s health is somehow compromised, though dead twigs might be too small to cause any threat to a climber. Large numbers of dead branches located high in the treetop usually tells you 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 or fungus growing on a branch also indicates a dying or dead branch.
The most 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, be shaken down while climbing, or be dislodged by a gentle touch. Climbers of wild trees must be constantly aware of these 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.