The trees in your landscape are an asset to your home. However, if neglected or improperly cared for, your trees can become a liability. Damaged trees can easily become hazardous. When a tree becomes hazardous, it often fails, which means a limb falls out of the canopy of the tree, the trunk splits and falls to the ground, or the entire tree becomes uprooted. Hazardous trees can cause injuries and property damage. If you have a tree that you think may be hazardous, seek professional help from an ISA Certified Arborist.
Because trees are living organisms growing in varied dynamic environments, it is impossible to predict exactly when a tree will fail, but keeping your trees safe from causes of damage is an integral part of tree care.
Natural Causes of Damage
Old senescent trees are more likely to fail than young vigorous trees. Size can also be a factor; large trees or branches are more dangerous when they fail. Mature trees in decline are more likely to become damaged due to their size and condition.
While uniquely-shaped trees may be visually interesting, shape may also indicate whether a tree is weak or structurally unbalanced. Storms, improper pruning, topping, and other damage can all weaken a tree’s architecture and cause unusual growth patterns.
Trees with multiple trunks or several branches attached to the same point on the trunk are at higher risk for splits or cracks. Tight V-shaped forks are more prone to break than open U-shaped unions. Inspect branches where they attach to the trunk.
Trees do not necessarily grow straight up. However, trees with a significant lean can indicate a problem. Look for cracked soil and exposed roots around the base of the tree, which may indicate the tree has recently begun to lean.
Weather often plays a role in tree failure. Extreme wind, rain, snow, and ice can cause perfectly healthy trees to fail. However, the trees that already have some defect, decay, or damage are usually the ones that fail under extreme weather events. Weather failure is often created by unintentional human mistreatment.
Trees in the home landscape often get planted incorrectly. If a tree is planted too deep or too shallow, in poor soil conditions, or without a big enough planting hole, it will never grow into a normal, healthy tree. This picture shows the twine string holding the burlap around the root ball was never removed when the tree was planted. Ultimately, this strangled the tree and killed it. Proper planting techniques are important to give trees a good start in the landscape.
Flush cuts or stub cuts are both common pruning mistakes that damage trees and often lead to the tree becoming hazardous. Topping, or indiscriminate cuts on large branches in an attempt to lower the height of the tree, is a particularly egregious error. A topped tree is much more likely to break apart during a storm than a tree with a natural growth pattern. Learn how to correctly prune your trees.
Grade Changes and Soil Disturbance
Changing the grade around the base of a tree by adding or removing soil may seriously disturb the delicate and vital relationship between roots and soil, affecting the tree’s health, soundness, and structural strength.
When fill from digging is added over existing soils, air and water that are essential for normal root functioning may be blocked. As a result, roots are smothered and die. Soil piled around the trunk may lead to conditions at the base of the trunk that invite rot, disease, and pests into the tree, compromising its health and safety. Even stockpiling mulch or soil in the Critical Root Zone of a tree for as little as several days can have severe, long-term effects, though it may take them years to appear.
Less damage to a tree’s roots is likely when the grade is lowered than when it is raised, unless a great deal of the root mass is exposed or removed. Removing one to two inches of soil normally will not affect a tree adversely, especially if steps are taken to ensure that drought damage does not result from loss of roots or root cover.
Neglect of newly planted trees will cause them to struggle and not grow properly. Mulch, watering, and protection from interference are important in order for a new tree to survive and thrive.
Garage or other chemical runoff such as oil, gasoline, paint, paint thinner, or other chemicals can contaminate the soil and poison trees.
Home maintenance and repair projects can damage tree limbs or trunks through accidents or lack of knowledge. Building a new home or an addition, putting in a new driveway or sidewalk, or trenching for utilities are all common construction activities that can put trees at risk. Never attach wires, cables, electrical conduits, mailboxes, or other objects to trees. Lawn mowers, weed whackers, and pets can damage the bark.
Severing roots, changing the grade of the ground, and other Critical Root Zone incursions usually lead to the decline and death of mature trees. Although this damage sometimes doesn’t appear until several years after construction, damage to tree roots is the number one killer of trees in the home landscape.
Automobiles, heavy equipment, and livestock can compact the soil, removing the roots' ability to nourish the tree. Remember that most of a tree’s roots are within the top 18 inches of soil.