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Managing a Hollow 100-Year-Old Maple: Foam, Fertilizer, and Risk Assessment

Understanding the Hollow

Decay fungi hollow the dead heartwood; living sapwood remains functional. The tree has likely been hollow for decades, surviving storms. Tar or cement fills damage living tissue and trap moisture.

Recommended Approach

Expanding foam in the skyward hole reduces water entry, slowing decay. Keep flush with bark.
Fertilize annually: 10-10-10 at 1 lb per inch trunk diameter (circumference ÷ 3.14 = diameter).
Monitor crown health: Full, healthy foliage = structural stability. Thinning crown = rising risk.

When to Remove

If a major hollow limb fails, assess hollow extent upward. But currently, the tree's longevity suggests good compensatory strength.

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