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Black Walnut Fern-Like Growth: Harmless Lichens, Not a Disease

Identification

"Fern-type growth on trunk and limbs" = lichens. Epiphytes—air-fed, not parasitic. Slight negative effect only if canopy very thin.

Management

If canopy full and green: ignore.
Fertilize: 10-10-10 at 1 lb/inch trunk diameter, before rain. Repeat fall.
Denser canopy naturally suppresses lichens.

No Removal Needed

Scrubbing damages bark. Lichens indicate good air quality.

Plant Diseases: Lichen on Mulberry Tree: Symptom of Underlying Stress; Lichens on Trees: Harmless Indicators of Stress, Not Disease; Black Blotches on Mulberry Trunk: Likely Lichens, Not Disease; Sugar Maple Lightning Strike and Lichens: Damage Assessment; Green Shamrock-Like Growth on Trees: It’s Likely Lichen, Not a Threat; Gray Marshmallow Masses on Tree: Harmless Lichens; Lichens on Weeping Cherry: Harmless Indicators of Thin Canopy; Lichens on Trees: Harmless Epiphytes or Hidden Threat?; Gray Fungus on Large Trees: Lichens, Not a Disease; Lichen on Orange Tree: Symptom, Not Cause

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