If you have large trees on your property, I’m sure it has crossed your mind- what if this tree comes down on my house in a storm?
Large shade trees provide so much benefit to properties. They shade homes, lowering energy costs. They bring beauty, increase property values, and attract beneficial wildlife. They sequester carbon, improve air quality and manage stormwater runoff. They also carry an inherent risk of failure in storm events. Strong winds and heavy loads from snow and ice can cause breakage of limbs or even whole trees. Knowing what to look for and having an ISA Certified Arborist regularly check your trees can help you avoid impending failures. Although even the healthiest and strongest of trees can come down in straight line wind events or tornadoes, most tree failures occur at structural weak spots on trees. Many structural defects can be seen and addressed before disaster hits. This is why it is so important to have an arborist check your trees periodically.
What to look for:
Arborists are trained to recognize what structural defects in trees are more likely to lead to failure. We all share and build upon decades of experience to understand and predict defects that have a high likelihood of failure. We call these failure profiles. Different species of trees fail in different patterns. For example, Eastern White Pines commonly have large horizontal branches break off during heavy events. Silver Maples may drop large branches where they have narrow branch attachments, and some species are more susceptible to failure in saturated soils. Below are some common structural deficiencies.
Bark Inclusions: Bark inclusions occur where two trunks or branches come together at a narrow angle. When small, this narrow attachment point may not be a problem, but as each trunk or branch grows larger, they start to grow into each other. The bark from each trunk or branch is trapped together and starts to decay. This is a very common point of failure for many tree species. To prevent bark inclusions, arborists will either remove or subordinate one of the branches. These weak points can be avoided with regular structure pruning of the tree from a young age. If the branches have already grown large, another option is to install a steel cable between the two branches to reinforce the weak point.
Narrow Branch Attachments: Even without a bark inclusion, narrow, v-shaped branch attachments can be a point of failure. In general, branch attachments are considered strongest when there is a significant size difference between branches and the attachment point is u-shaped. Regular structure pruning from a young age can remove or prevent narrow branch attachments.
Dead, Broken, Or Hanging Branches: If you notice that your tree has branches with no leaves, dead leaves, or a branch that is hanging downward from being broken, the odds of those branches falling and damaging someone below is increased. The risk is failure ranges based on the size and the species of tree, but consider what a dead or broken branch will hit if it falls. Dead and broken branches should be pruned out to avoid failure.
Overextended Branches: Overextended branches are those that grow beyond the silhouette of the rest of the canopy. These extra-long branches are more likely to take higher forces from wind, rain, and snow loads. If you consider how a lever works, longer levers apply more force to the base, just as longer branches do. These branches can be safely shortened back to reduce their loading and thus their odds of failure.
Injuries and Cankers: Injuries on a tree refer to any mechanical damage or wounding that may kill the bark. Cankers are often fungal or bacterial infections that also lead to the death of bark on a tree. Bark or outer wood of a tree that is dead or damaged becomes structurally weaker. If more than one third of the trunk circumference is damaged by injury or canker, the odds of failure will increase. An arborist can assess how much a risk injuries and cankers may be, and can provide treatment plans to help the tree seal over wounds.
Internal decay: Decay in trees is very common, but is not necessarily a reason to remove a tree. The risk of failure from decay can vary hugely depending on the species, the location and extent of decay, the health of the tree, and the species of decay fungi. Internal decay cannot typically be visually assessed. Arborists will often look for signs of decay, such as swelling, ridges, carpenter ants, and mushrooms. There are other tools that we use to better assess the extent internal decay in trees, like resistance decay detection drills. We use these tools to better assess the risk of failure due to loss in wood strength. Always reach out to have one of our TRAQ certified Arborists assess your tree if you suspect decay.
Basal or Root Decay and Saturated Soils: Roots are what anchors your tree to the ground and prevent the whole things from toppling over. Injuries and decay in root systems can be hard to assess. Roots may undergo injury during construction and remodeling projects, and decay may take years to set in after. Death of roots during flooding or drought conditions may also lead to root rot or root decay that can destabilize trees. Flooding and heavy rains pose additional risks for shallow-rooted trees. When the soil becomes saturated, tree roots may not be able to anchor trees as well. If your tree has a buried root collar, this may increase the rate of decay at the base of the tree. Girdling roots may also lead to the death of bark at the base of the tree, leaving an opportunity for decay to set in. Avoid injuries to surface roots while mowing the lawn. This is a very common source of decay entering tree roots or root collars.
Regular monitoring and pruning of large trees on your property can prevent some structural deficiencies from forming. Pruning and cabling options can also correct existing issues or reduce the risk of failures. If you think your tree has one or more structure defects, reach out to Tree Health management to have an ISA Certified Arborist assess your tree. If your arborist determines that visual assessment is not enough, further testing from our TRAQ Certified Arborists can determine the risk level of your tree failing and provide risk mitigation plans. Keeping your trees healthy with property cultural practices of watering and mulching can go a long way to prevent future issues as well.