By Scott Gardner

When a severe storm strikes, immediate visible damage often includes downed power lines and flooding. Yet, what may surprise some is that the full impact of storms can remain concealed within trees for an extended period.

These trees, harboring hidden damage, are occasionally dubbed “zombie trees.” Much like the zombies in horror films, these trees have the potential to inflict substantial harm if not detected early. Fortunately, there are methods to identify the warning signs.

What is a zombie tree?

A zombie tree is a tree that appeared undamaged immediately after a storm or drought, but is now beginning to display symptoms of distress. While some of these trees might be salvageable, others could be deteriorating from within and necessitate removal. The deceptive aspect of zombie trees lies in their ability to appear safe in the days immediately following a storm or significant weather event, potentially posing a hidden threat to unaware property owners.

How to spot a zombie tree

• Dead wood or decay: dead trees or large, dead branches can fall at any time.
• Cracks: deep splits through the bark that extend into the wood of the tree’s trunk or limbs.
• Heavy canopies: excessively thick branches and foliage catch more wind during stormy weather. This increases the risk of branch breakage and uprooting. 
• Discolored foliage: heavy flooding will cause leaves to wilt or dieback early. 
• Root problems: check if the soil near the tree’s base is lifting on one side. If construction has occurred nearby, closely examine that area of the tree. Nearby construction may sever large roots or compact the soil, reducing root growth. Without a strong root system, trees are more likely to be uprooted or blown over in storms.
• Poor tree architecture: excessive leaning of the tree or branches growing out of proportion with the rest of the tree crown. Odd growth patterns may indicate general weakness or structural imbalance.

What to do about zombie trees

• Identify issues early to prevent damage before it happens with a home tree health check. With early action, you may be able to save a tree. Walk around the yard, inspecting trees for dead wood or decay, cracks in the bark that extend into the tree’s trunk or limbs, discolored foliage, and root and architecture problems. Is the tree lifting on one side or leaning excessively? That could be a sign of trouble.

• Get an expert opinion. If you notice any issues during the tree health check, call a certified arborist. Certified arborists can address problems visible to the naked eye—plus damage you may not be aware of—and help you decide on a plan of action. Homeowners should always check for TCIA Accreditation, ISA Certification, proof of insurance, WorkSafe BC coverage, and a list of references when hiring a certified arborist.
• Know your options. Although defective trees are dangerous, not all of them need to be removed immediately. First, understand a tree’s risk level. Some defects can be addressed to prolong the life of the tree, and some of the care and maintenance can be done by homeowners. Important tree maintenance tips include fertilizing, planting suitable trees and shrubs for our local climate, and proper pruning.

Zombie trees are a hazard—but unlike their namesake, they don’t have to cause fear and panic. By giving your trees the attention they need, you won’t have to worry about your yard turning into a scene from The Walking Dead.

Scott Gardner is district manager of Davey Tree Expert Co. of Canada Ltd.