Lichen Growth on Rose of Sharon: Harmless or Harmful?

Lichen Growth on Rose of Sharon: Harmless or Harmful?

A rose of Sharon tree has lots of moss-like growth on the trunk. The owner asks if it can be pulled off and how to prevent it.

It's Not Moss—It's Lichen

Lichens are a symbiotic partnership of a fungus and an alga (or cyanobacterium). They are epiphytes—they grow on the bark but do not penetrate it or take nutrients from the tree.

Why They Appear

• Lichens thrive on slow-growing, mature, or stressed trees with open canopies.
• They need light; a dense canopy shades them out.
• They also grow on rocks, fence posts, and dead wood.

Can You Remove Them?

Yes, you can gently rub or brush them off when the bark is dry. However, they will return if the underlying conditions (thin canopy, high light on bark) persist.

Real Solution: Improve Tree Vigor

• Water deeply during drought.
• Fertilize appropriately in early spring.
• Prune to improve structure and encourage dense foliage.
• Mulch properly (2–3 inches, not against trunk).

A vigorous tree with a full canopy will naturally suppress lichen growth. Lichens are a symptom of reduced vigor, not the cause of decline.