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River Birch Trunk Rot After Improper Pruning

River birch with 3 trunks (5-inch diameter each). One cut to 3 feet 2 years ago; stub rotted 1 foot down, 3–4 inches wide. Owner fears losing tree or patio damage.

Cause

Leaving a long stub prevents wound closure. Decay fungi entered stub, now in main trunk base. Can spread to other trunks, weakening structural roots.

Management

Fertilize with 10-10-10 at 1 lb/inch trunk diameter (fall + spring) to boost root health and compartmentalization.
Monitor for leaning/cracking at base of remaining trunks.
If instability appears, remove tree.

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