Technical Summary: Structural Defects & Included Bark

/ by Jon Smith / in Blogs

Technical Summary: Structural Defects & Included Bark

Risk Profile: Included bark is one of the most common causes of catastrophic tree failure. It represents a significant structural defect where a mechanical “seam” replaces the solid wood connection necessary to support branch weight and wind load.

Understanding Included Bark

In a healthy branch union, the tree produces a “branch bark ridge” or collar—a visible bulge of wood that acts as a structural reinforcement. In cases of included bark, the bark grows inward into the crotch of a V-shaped union. This creates a physical barrier that prevents the wood fibers of the two stems from knitting together, resulting in a joint held together by gravity and friction rather than biological strength.

Identification & Visual Indicators

Early identification of these weak unions can prevent structural collapse. Look for these three primary signs:

  • Deep Seams or “V” Formations: A distinct line where the bark folds inward at the joint. Unlike a strong “U” shaped union, a “V” shape indicates that the stems are pressing against each other rather than growing as one.

  • Absence of Branch Collars: A lack of an outward woody bulge at the base of the branch. This suggests there is minimal “bridging” wood holding the union together.

  • Seepage & Staining: Dark stains or moisture oozing from the seam. These crevices often trap organic debris and water, creating a micro-environment for decay.

Mechanical & Biological Risks

Risk Factor Impact on Tree Integrity
Structural Failure High winds, snow, or ice loads apply leverage to the weak union, often resulting in a vertical split down the trunk.
Weak Attachment Because bark-to-bark contact has no structural strength, the branch essentially “rests” against the trunk rather than being part of it.
Pathogen Entry The trapped moisture and debris within the seam provide an ideal entry point for carpenter ants, fungi, and moisture-driven rot.

 

Mitigation & Management

Included bark does not always require tree removal, but it does require professional management to mitigate risk.

Recommended Actions:

  • Targeted Pruning: Reduction pruning can decrease the weight and “sail area” of the affected limb, reducing the leverage placed on the weak union.

  • Supplemental Support: In high-value trees, an arborist may install Cabling or Bracing systems. These steel or synthetic lines redistribute the load to stronger parts of the tree.

  • Professional Assessment: Have Big Heart Tree Care evaluate the “depth” of the inclusion to determine if the tree is a candidate for preservation or if the risk of failure near structures is too high.