Identifying Harmless Lichens on Tree Bark

Green Growth on Trees: Lichens, Not Disease

The green, gray, or yellowish growth on your Ohio trees' bark is lichen—a symbiotic organism of fungus and algae. Lichens are not parasitic; they use the bark only as a substrate. Their presence indicates good air quality, as they are sensitive to pollution.

No Treatment Needed

Lichens do not harm trees. They thrive on slow-growing or stressed trees but are not the cause of decline. Improve tree vigor with proper watering, mulching, and fertilization if needed. Enjoy them as indicators of a healthy environment.