White Growth on Lilac Trunks: Likely Harmless Lichens

A 7-foot lilac bush shows white mold-like growth on lower thick trunks, starting 1-2 inches above ground. Higher branches are unaffected. The description matches lichens—symbiotic organisms of fungi and algae that commonly colonize bark.

What Are Lichens?

Lichens are not parasites; they do not harm the plant. They simply use the bark as a substrate. Their presence often indicates good air quality. They are especially common on lilacs and many other woody plants.

No Treatment Needed

No action is required. The lilac's health is unaffected. For confirmation, refer to the Ohio State University fact sheet on lichens (HYG-3312-09). Focus instead on proper cultural care: adequate sunlight, well-drained soil, and appropriate pruning.