Lichens on Crepe Myrtle: Why That 'Mossy Fungus' Is Actually a Good Sign

What You're Seeing

The "mossy fungus" on your 12-year-old crepe myrtles is lichens—a symbiotic partnership of a fungus and an alga (or cyanobacterium). They are not parasitic and do not harm the tree.

Lichen Biology

• Fungus provides structure, absorbs water/minerals.
• Alga provides carbohydrates via photosynthesis; some fix nitrogen.
• Forms: flat, leafy, or hairlike. Colors: white, gray, green, yellow, red, black.

What Lichens Indicate

Lichens thrive in clean air. Their presence means relatively pure atmosphere. They proliferate on dead/dying branches due to increased light, not because they killed the branch.

Recommendation

No treatment needed. Fertilize the tree to maintain vigor. If lichens are unsightly, they can be gently brushed off, but they will return.