Common Structural Deficiencies in Trees

The problem:

• A deep split through the bark, extending into the wood of the tree reduces the integrity of the wood and can lead to other issues like deeper cracks and breakage, fungus, disease, and pests.
• Some cracks are internal and don’t show through the bark, making them seem deceptively strong.
• Cracks are considered dangerous because they indicate that another part of the tree has already failed.

The solution:

If a crack extends deeply into or through the stem, two or more cracks occur in the same area of the stem, a crack comes in contact with another defect, or if a branch of sufficient size to cause injury is cracked, call an experienced tree care professional. In some cases, the arborist may install a cable or brace system to support the weakened area of the tree. If the tree is not salvageable due to other underlying issues, your tree company may recommend heavy pruning to reduce risk, or removal.

The problem:

• Branches that are not firmly attached to the tree are a fall risk and could potentially injure a person or damage property.
• Bark grows between the branches or the branch and trunk, inside the union. The ingrown bark does not have the structural strength of wood and may act as a wedge forcing the union apart.
• Elms and maples often produce weak branch unions as those trees have a tendency to form upright branches.
• Weak unions are likely to form after a tree or branch is improperly tipped or topped, causing the stub to decay. Improper pruning techniques provide poor support for new branches that usually develop along the cut branch.

One notable type of weak union is a fork. This defect appears visually to be a crack but is actually formed when a bi- or tri-furcated (double or triple leaded) tree has leads that grow too close together, causing a weak union (see next). As the tree grows and widens over time, the layers of wood and bark grow into each other in a way that is structurally weak. This can cause pressure build-up and eventual splitting of the leads.

The solution:

Not all branches that grow close together are an imminent threat. If a weak branch union occurs on the main stem, the union is cracked, or is associated with a crack, cavity, or other defect, call an experienced tree care professional. They will be able to assess the issue and provide next steps.

The problem:

• Wood that is soft or crumbly is not strong enough to support the weight of the tree.
• Decay is often a sign of other major problems and is often the last symptom before tree death.
• Decay can cause cavities and cracks, and lead to infestations of insects and animals.

The solution:

Sometimes strong trees, like oak, that experience decay can stay standing for years after the initial diagnosis. Due to the volatile nature of this structural deficiency, its best to leave the decisions to your arborist who has experience in dealing with advanced stages of rot. 

The problem:

• Cankers are symptoms of injury often associated with an open wound (such as a pruning cut) that became infected with fungus or bacteria. The tree may develop tissue around the wound that is similar to a cyst, to separate the healthy and infected tissues. However, as the infection spreads into bark, sapwood, and the vascular system, the tree may experience leaf die back or malformed leaves.
• Cankers come in many colors, shapes, and sizes and can be difficult to identify. If left to persist, they can lead to further infection or rot.
• An infected tree is susceptible to other pest infestation or disease.

The solution:

The best controls for cankers are preventative ones. Proper pruning techniques, mulching practices, and water and soil management to keep plants healthy is the best way to prevent injury that leads to cankers. There are no chemicals universally registered for canker treatment. If the canker forms on branches or twigs, the branch may be removed several inches from the canker to prevent spread. Trunk canker removal poses more of a risk and should only be done by an experienced tree care professional.

The problem:

• Issues in the roots of a tree can cause issues in the canopy too. Tip dieback, leaf loss, and discolored leaves can all be signs of root problems.
• Issues like girdling roots, which can be caused by soil or mulch mounding, can lead to root strangulation and reduced nutrient and water flow through the tree.

The solution:

One of the easiest at-home solutions to prevent root issues is to do proper maintenance on your trees. Avoiding mounded soil and mulch, proper water and soil management, pest control, and regular assessments can all help prevent problems and catch early signs of developing issues. Call an experienced arborist if you have any concerns about the roots of your tree.