What are codominant stems?

Codominant stems occur when a tree develops two or more main trunks of similar thickness from the same base or junction point. Rather than one clear central leader, the tree splits into competing branches that grow upward side by side. This differs from normal branching where smaller limbs extend from a single dominant trunk.

Arborists flag codominant stems as a structural concern because the junction where they meet is inherently weak. The angle of attachment, bark inclusion (where bark gets trapped between the two stems), and the way the tree distributes weight across the split make this junction prone to failure. Under heavy snow, ice, or wind loads that Westchester County trees regularly face, codominant stems may split apart, even if the tree is otherwise healthy.

Trees with codominant stems can grow well for years, but the risk of sudden limb separation increases as they age and become heavier. During a tree inspection, certified arborists assess whether codominant stems pose an unacceptable hazard. Management options depend on tree size, age, and location, but the structural defect itself remains a permanent concern that should be monitored or addressed. Homeowners who notice this pattern on their property should have an arborist evaluate the risk.