What Is Included Bark?

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Included bark is one of the most common structural defects in trees—and one of the leading causes of sudden failure.

Included bark is one of the most common causes of tree failure in Fort Hunt, Alexandria, and Mount Vernon, Virginia.

It forms where two stems grow together but never properly bond—creating a hidden structural defect that can split without warning.

Most homeowners don’t recognize it until the tree begins to fail.

This Mount Vernon tree shows co-dominant stems with a developing crack at the union. While it may look stable from a distance, the internal structure is weak and under constant pressure.

As the stems grow, they push against each other, increasing the risk of splitting—especially during storms or heavy wind.

 Included bark is one of the leading causes of tree failure in Alexandria and Mount Vernon, VA. 

 Included bark forms when two stems grow together and trap bark between them instead of forming strong connective wood.

This creates a weak union where pressure builds over time. As the stems increase in size, they push against each other, increasing the risk of splitting—especially during storms or heavy wind.

In this Real Mount Vernon example, the union is already showing signs of stress and early separation.

 This close-up shows a tree with included bark where the union has already begun to separate.

Moisture, decay, and internal pressure are accelerating the failure process. Once a crack like this forms, the likelihood of stem separation increases significantly—especially during storms.

This is no longer a theoretical defect. This is active structural failure.

This is a real tree in Mount Vernon, Virginia. 

Included bark prevents the formation of strong connective wood between stems. Instead of interlocking fibers that distribute load, the union is held together by compressed bark, which cannot support structural stress. As the tree grows, this trapped bark acts like a wedge, forcing the stems apart and concentrating pressure at the union. Over time, this leads to internal cracking, reduced load-bearing capacity, and a significantly higher likelihood of sudden failure.  Research from the International Society of Arboriculture shows that included bark significantly reduces structural strength at the union. Once a crack like this forms… 

Failure is often sudden and without warning once separation begins. 

Included bark cannot be reversed, but the risk it creates can often be reduced.

In situations like this, arborists may recommend installing a cabling system to limit independent stem movement and reduce stress at the union. Combined with selective pruning to reduce end weight, this approach helps stabilize the structure and lower the likelihood of failure.

The goal is not to eliminate the defect, but to manage it—extending the safe, functional life of the tree while reducing risk to nearby structures and people.

This is a real tree in Mount Vernon, Virginia, where early intervention can make a significant difference.