Is that branch dead or alive?
Fall has come and most or all the leaves are off your trees. A common question we hear is, how can you tell what is alive and what is dead? In short, the characteristics of dead branches are different than live branches. A deeper look will help you understand what we as arborist use as clues when deciding what to remove and what to keep.
The first major difference is visibility. When you are on the ground looking up at a tree branch 20 feet or higher in the canopy it may be difficult to see a lot of detail. As arborists, we look at trees all day long and have trained our eyes to recognize signs of dead branches from a distance. Our production crews are able to further distinguish dead from live branches because they are going to be accessing the canopy which means they won’t be 20 feet from the branch questioning its health, they will be right next to it, touching it, examining it. It is a lot easier to tell the health of a limb when it is in your hand than when it is far away.
As we begin to access the tree and work in it, the tree responds with movement. Dead branches move differently than live branches. If we are climbing the tree, our movement and the reaction by the tree is enough to identify where we need to focus our attention. When branches die they become less flexible and more brittle. Branch movement plays a major role in how trees deal with load (wind, rain, snow). The movement dissipates energy and results in less force that the tree needs to attenuate. Tree branches that don’t move are at a greater risk of breaking (i.e. dead branches fail more often than live ones). This also works in our favor for identifying dead branches. When a branch moves differently or moves less than the surrounding branches it is likely to be a dead branch.
When tree parts die they begin to breakdown by means of fungal decomposition. Ever see a mushroom growing on a tree? Mushrooms are the fruiting body of fungus. When mushrooms are visible on a branch it is likely dead or in some level of decay. As a word of caution when mushrooms appear on the trunk or around the base of a tree, you should have the tree looked at by an ISA certified arborist as soon as possible. When mushrooms are seen on branches it is a good sign the branch needs to be removed. Some mushrooms are very small and can be best identified while we are near them, working in the canopy.
Bark serves many purposes; retaining moisture content for the living tissue, regulating temperature, and protecting the inside of the tree from the outside elements, to name a few. When a branch dies the bark no longer serves a purpose and is eventually shed from the tree system. During this process bark may become discolored before it is shed. When we are close to dead branches, different color bark or missing bark is an easy clue that the branch is dead and needs to be removed.
Buds are the trees future branches, leaves, and flowers. When a branch has buds, seeds or leaves on it we can assume it is still functioning properly. If the buds are missing from a branch it is likely dead and can be removed. Buds on some trees are extremely small and hard to see, like the redbud or birch trees. Even healthy and live branches can be difficult to tell just looking at buds. However some species like oaks, ashes, and basswoods have large obvious buds that are easier to see. Again buds are easier to see when viewing branches up close.
Branches are green!? Well not at first sight. Bark is usually on a scale of grey but just under the bark exists a layer of chlorophyll filled, green, photosynthetic cells. This helps the tree produce energy for itself when it has no leaves. When a branch is dead it doesn’t maintain this layer and the green disappears. A scratch test can be performed on young branches and thin barked trees to look for evidence of health. With your fingernail, you can scratch the surface of the bark and if the resulting color underneath is green the branch is likely alive, if the under color is not green it may be dead. This test should be used infrequently as it does remove a small section of bark and can result in injury.
Using the above mentioned clues to assessing branch health, we as arborists are able to identify which branches are alive and dead even without leaves. This helps us maintain your trees all year long and reduce our dependency on removing deadwood only when trees are fully leafed out. In fact, some trees are best pruned in winter. Structural pruning and pruning trees with seasonal disease concerns should be addressed in the winter. If you think your tree has dead branches that should be removed, don’t wait until summer, winter maybe the best time.
John Wayne Farber
Certified Arborist WI-0877A
Hoppe Tree Service