Why You Should Not Fill a Rotting Willow Tree Cavity

The Problem with Cavity Filling

Filling cavities (cement, foam, etc.) traps moisture, prevents natural compartmentalization, and weakens the tree. Modern arboriculture advises against it.

Natural Defense: Compartmentalization

Trees wall off decay with chemical/physical barriers. Willows are "poor compartmentalizers"—decay spreads fast.

Correct Approach

• Leave cavity open.
• Do not drill drain holes.
• Improve overall tree health (water, mulch, avoid injury) to boost natural defenses.

Key Takeaway

A healthy tree is the best defense against cavity decay. Filling does more harm than good.