Owen Tree Service

Tree Risk Assessment

Owen Tree Service: Your Trusted Arborists in Michigan

Trees: Valuable Assets with Potential Risks

Trees add beauty and value to landscapes, serving as key components of well-designed properties. Beyond their aesthetic appeal, trees play a significant role in sustainability, with millions being planted in the U.S. to reduce pollution and enhance urban and suburban environments. However, along with their value comes the potential cost of maintenance and, in some cases, the risk of injury or property damage if a tree fails. Tree failures typically fall into two categories: 

  • Extreme, unpredictable conditions.
  • Failures due to obvious structural weaknesses in the tree.

The Unpredictability of Tree Failure

Extreme weather events like tornadoes, hurricanes, and ice storms can cause even healthy trees to fail. According to The Weather Channel, ice can increase the weight of branches by thirty times. Trees do not naturally develop to withstand such rare weather conditions, meaning any tree, regardless of its age, species, or condition, can fail in these circumstances. While extreme events are uncommon, they are often catastrophic. More commonly, however, trees fail under normal conditions when their structure is compromised. 

Identifying Structural Weakness in Trees

Throughout their lives, trees sustain damage, disease, or decay. The key question isn’t whether a tree has some damage but rather how much, where it’s located, and whether it weakens the tree’s stability. Tree failure isn’t always an unavoidable "act of God." If a tree shows obvious signs of decay or structural weakness, its integrity should be questioned. Common signs include: 

  • Cavities at branch wounds or on the trunk or roots 
  • Fungal growth on or around the tree 
  • An excessive number of dead limbs 
  • Cracked limbs or trunks, especially if oozing 
  • Fallen branches larger than 2 inches in diameter 

Even apparently healthy trees can be blown over in high winds. 

With visible trunk decay and a fungal fruiting body growing at the base of the branch, this branch failure could have been easily predicted.

Trunk decay and woodpecker damage will likely lead to this tree trunk failing under high winds.

Canker on a tree trunk will cause a structural weakness.

Does a Hazardous Tree Mean Danger?

Not necessarily. There are two main factors to consider: 

  1. Trees naturally shed dead limbs, and wood decay is common in older trees. Defects do not always indicate imminent failure, as trees are resilient organisms.
  2. Risk is more about what the tree could impact if it fails. A tree may be structurally compromised but pose little risk if it’s in an area with no valuable structures, vehicles, or people nearby.

It’s best to consult an arborist before a tree fails. Regularly inspect trees near your home or other targets, especially after storms. Large trees near houses or driveways should be professionally assessed for risk. Arborists are trained to detect signs of structural weakness and can recommend ways to reduce the potential for failure. 

How to Reduce the Risk of Hazardous Trees

While internal decay cannot be treated, the risk of tree failure can be minimized by reducing stress on compromised wood. Some options include:

  • Young Tree Training: Early pruning helps establish strong tree structure. Pruning should be done soon after planting and continue regularly during the first 10-20 years. This ensures a single main trunk and well-spaced branches. 
  • Correcting Tree Form: If a tree wasn’t pruned properly when young, stress can be reduced by pruning competing trunks or reducing the crown size to lessen the load on weak areas. 
  • Storm-Proofing Trees: Removing weak limbs or reducing the canopy can reduce storm damage, preventing branches from ripping down the trunk or causing further injury. 
  • Crown Reduction: For trees with weak trunks or limbs, reducing the spread and height of branches lowers the risk of breakage. 
  • Cabling and Bracing: Arborists can install cables and rods to support weak limbs or trunks, following industry standards for safe placement. 
  • Removing the Target: In urban settings, it may not be possible to remove targets like buildings or vehicles, but where feasible, moving valuable items away from compromised trees can reduce risk. 

The Importance of Regular Tree Inspections

Regular inspections are an essential part of tree maintenance. Early detection of structural defects or damage can prevent further issues. For property managers, keeping written records of tree inspections can help demonstrate proper care, especially in the case of injury or damage during extreme weather. 

Arborist using a Resistograph to detect internal decay.

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