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Oak Tree Cavity Rot: Don't Fill, Fertilize Instead

An oak has rot in two old limb removal cavities. Filling with concrete, foam, or asphalt harms the tree by abrading compartmentalization walls and trapping moisture. Modern arboriculture: leave cavities open. The tree walls off decay via compartmentalization (chemical/physical barriers). Improve health to strengthen this defense: fertilize with 10-10-10 at 1 lb per inch trunk diameter now and late summer. Water during drought. No wound paint.

Cavity Management

Do not fill, drain, or scrape cavities.
Fertilize to boost tree vigor.
Monitor for structural weakness.

Trees: Variegated Willow Myrtle Death: Not Root Rot, Likely Pre-Existing Defect; Fir Tree "Dry Rot": Internal Decay, Not Fatal; Assessing Oak Trunk Decay: When to Worry About Heart Rot; Oak Trunk Decay: Management and Structural Support; Tree Cavity Care: Don’t Fill, Don’t Drain, Do Promote Health; Maple Trunk Rot from Old Pruning Wound; Lichens vs. Decay Fungi on Oak: Distinguishing Harmless from Hazardous; Tree Cavity in Deck Tree: Don't Fill, Fertilize; Historic Apple Tree Cavity: Leave Open, Boost Health; Filling Tree Cavities: Why Cement Harms Hollow Trees

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