Tree Cavity Care: Why Not to Fill Holes in Oaks

An oak has a large cavity from a past limb removal, holding water. The owner considers filling with concrete or asphalt. Research shows filling cavities harms trees: materials abrade inner walls, trap moisture, and prevent natural compartmentalization. Drainage holes worsen decay. Best practice: leave cavity open, remove loose bark, and improve tree health with fertilization and watering. A healthy tree walls off decay naturally. Cosmetic foam is optional but unnecessary.

Modern Cavity Management

• Do not fill, drain, or scrape cavities.
• Promote tree vigor with proper care.
• Accept that hollow trees can be structurally sound if healthy.