If you've ever noticed crusty, gray-green patches on a headstone, you've likely seen lichen. It's one of the most common — and most damaging — things that can grow on a memorial. Understanding what lichen is and why it matters can help you protect a loved one's headstone for years to come.
What Is Lichen?
Lichen is not a single organism — it's actually a partnership between fungi and algae (or cyanobacteria) living together. This unique combination makes lichen incredibly resilient. It can survive in harsh conditions, cling to bare rock, and grow without soil. That's exactly why it thrives on headstones.
Lichen grows very slowly — sometimes just a few millimeters per year — but it's persistent. A headstone that hasn't been maintained for a decade can be heavily colonized, with lichen covering much of the surface and obscuring inscriptions.
Why Is Lichen Harmful to Headstones?
It physically damages the stone. Lichen attaches to stone using root-like structures called rhizines that penetrate the surface. As the lichen grows and contracts with temperature changes, it slowly breaks apart the stone at a microscopic level — a process called biodeterioration.
It produces acids. Lichen releases oxalic acid and other organic acids as part of its natural processes. Over time, these acids etch into the stone surface, causing pitting and erosion that can permanently damage engravings and fine details.
It traps moisture. Lichen holds water against the stone surface, which accelerates weathering — especially in climates with freeze-thaw cycles. Water that seeps into small cracks and then freezes can cause the stone to crack or spall.
It's hard to remove once established. The longer lichen is left untreated, the more deeply it embeds itself into the stone. Early intervention is always easier and less risky than trying to remove mature lichen colonies.
Can You Remove Lichen Yourself?
It's best to leave lichen removal to professionals. Scraping or scrubbing lichen off a headstone without the right technique can pull away the stone surface along with it, causing more damage than the lichen itself. Pressure washing is also risky — the force can erode soft stone and drive moisture deeper into cracks.
Professional memorial care uses safe biological treatments and gentle cleaning methods that kill lichen at the root and remove it without harming the stone.
Prevention Is the Best Protection
Regular professional cleaning is the most effective way to prevent lichen from taking hold. Catching early growth before it matures means less damage and easier removal. An annual or biannual cleaning schedule keeps memorials looking their best and protects them for future generations.
Concerned About Lichen on a Headstone?
At Stone Guardians, we specialize in safe, effective headstone cleaning that addresses lichen and other biological growth. We exclusively use D/2 Biological Solution. The only cleaning solution approved for Arlington National Cemetery. If you've noticed lichen on a loved one's memorial, we'd be honored to help restore it. Contact us to learn more about our services: 800-410-7154