Green Blotches on Pine/Fir Trunk: Harmless Lichens

Green blotches on conifer trunks are lichens—symbiotic fungus/algae organisms. They're not parasites, don't harm trees, and indicate clean air.

Lichen Biology

• Fungus provides structure, algae provides food via photosynthesis
• Grow on bark surface only—no tissue penetration
• Colors: gray, green, yellow, orange, black
• Forms: crusty, leafy, shrubby

Why They're Beneficial Indicators

• Absent in polluted areas—your air is clean
• More visible on stressed trees (thin canopy = more light)
• Don't cause decline—colonize already-declining trees
• Town's tree removal was misguided—lichens didn't kill them

Action: None Needed

If foliage is green and healthy, tree is fine. Lichens are ecological neighbors, not enemies. Enjoy the biodiversity sign.