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To: Bluedot Living
From: Polly Hill Arboretum
Subject: Post-Storm Tree and Shrub Health Care: What Homeowners Should Know
After a major storm, it’s natural to walk your property and assess damage to trees and shrubs. Broken branches, split trunks, and bent shrubs can look alarming. Some damage can be safely corrected, while other situations require removing the entire tree to avoid long-term hazards. Understanding how trees respond to injury will help you make better decisions and keep your property safe.
Unlike people, trees do not “heal” wounds by replacing damaged tissue. Instead, they compartmentalize injuries, also known as CODIT, or compartmentalization of decay in trees. This means the tree forms chemical and physical barriers around the damaged area to limit decay and prevent it from spreading into healthy wood. Over time, new growth may roll over the wound edges, but the original damaged wood remains inside the tree. Because of this, the size and severity of the wound matter. Large wounds, especially those involving the trunk or main structural branches, can overwhelm the tree’s ability to compartmentalize decay. Also for CODIT to occur the wound needs to be in the presence of oxygen. Therefore, we do not recommend using any wound sealants.
When Is Damage Too Severe to Fix?
Some defects significantly weaken a tree’s structural integrity. These situations often require removal rather than repair:
- Large trunk splits or cracks
- Torn bark exposing a wide area of wood
- Broken codominant stems (two trunks of equal size splitting apart)
- Major branch failures that remove more than 25–30% of the canopy
- Damage located above targets such as homes, driveways, or walkways
Leaving a severely compromised tree in place creates a future hazard. Even if the tree looks stable immediately after the storm, decay can spread inside the wood. Months or years later, the weakened area may fail unexpectedly — potentially injuring someone or damaging property. It’s better to remove a high-risk tree early than to wait for a dangerous failure.
Example 1: Small Tree with a Codominant Trunk Break
Imagine a small ornamental tree with two equal trunks growing from the same point. A storm breaks one trunk halfway up. In this case, the proper corrective action is to remove the broken trunk entirely, cutting it back to the point where it joins the remaining stem. The cut should be made just outside the branch collar. Avoid leaving a stub, but do not cut flush into the remaining trunk. Once the damaged trunk is removed, the remaining stem can often assume dominance. The tree will begin compartmentalizing the wound by forming protective barriers around the cut. Over time, new growth may close over the wound. Because the tree is small, the wound size is manageable, and the tree can often continue growing safely.
Example 2: Large Tree With a Torn Branch and Trunk Damage
Now consider a mature shade tree where a large limb breaks during a storm and tears downward, ripping bark and wood from the trunk. This type of damage creates a long vertical wound and exposes a large amount of internal wood. Even if the broken branch is removed cleanly afterward, the trunk injury remains. The tree cannot restore structural strength to that torn area. This defect often leads to internal decay and a permanent weak point in the trunk. In a large tree, especially near a house or driveway, the risk of future failure is high. Because the damage compromises the main structure of the tree, removal of the entire tree is typically the safest option.
Most Common Snowstorm Damage
During heavy snowstorms, the most common damage is branch bending and breakage. Wet, heavy snow accumulates on leaves (in evergreens) and fine twigs, adding significant weight. This often leads to:
- Broken outer canopy branches
- Split codominant leaders in small trees
- Bent or splayed shrubs
- Evergreen branches permanently drooping
Shrubs and small trees sometimes rebound once snow melts, but broken branches should be pruned cleanly to prevent decay.
When to Call a Professional
If damage involves large branches, the trunk, or trees near structures, consulting a certified arborist is strongly recommended. They can evaluate structural integrity and determine whether corrective pruning or removal is safest.
Taking prompt, informed action after a storm helps your trees recover when possible — and ensures that hidden defects don’t become hazards later.
