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Lichens on Oak and Roof: Harmless Epiphytes

What They Are

Light green scaly growth on oak bark and asphalt shingles is lichens—a symbiosis of fungi and algae. They are epiphytes, not parasites; they make their own food.

On Trees

Slight negative effect only; indicate thin canopy.
Best control: fertilize to thicken canopy (10-10-10 at 1 lb/inch trunk diameter).
Baking soda spray (0.4 lb/gal) kills lichens but is rarely needed.

On Roofs

Lichens hold less moisture than moss; less damaging.
Clean annually with hose; scrub with oxygen bleach solution if desired.
Install zinc strips at ridge to prevent regrowth.
Vinegar spray kills lichens; scrub off after.

Trees: Lichens on Oak Trees: Harmless Epiphytes or a Sign of Stress?; Greenish-White Scale on Oak: Lichens, Not a Disease; Nuttall/Shumard Oak Lichen: Not Harmful but Indicates Stress; Oak Leaf Galls: Wasp-Induced, Cosmetic Only; Oak Trunk Fungus (Conks): Decay Fungi Management; Gray Fungus on Large Trees: Lichens, Not a Disease; Dark Clusters on Oak Branches: Insect Galls, Not Fungus; Decay Fungus Conks on Red Oak: Not an Emergency; Carpenter Ants and Decay in a Mature Oak: What to Do; Orange Mushrooms on Oak Trunk: Decay Fungus, Not an Emergency

Garden Articles

Green Flat Fungus on Oak Trunk: Likely Lichens—Harmless, but Photo Needed for Certainty

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Orange Bumps on Oak Leaves in Florida: Likely Gall Insects

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Water Oak Brown Fungus: Need Photos for ID

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Lichens on Trees: Harmless Epiphytes or Hidden Threat?

Lichens on Transplanted Live Oaks: Cosmetic Concern, Not a Threat

Transplanted Oak Tree with Top Dieback: Assessment and Care