What is Biological Growth? Removing Lichen, Mold and Algae from Grave Markers

Green tints, crusty grey patches and black spots are living organisms, not dirt. Here is what they do to stone and how to remove them safely.

What this article covers

• Lichen roots into the stone and holds moisture against it
• D/2 breaks the organism down and keeps working for weeks
• Scraping tears away the weathered surface with the growth
• Never use pressure washers on biological growth

Every memorial is different. Stone type, age, exposure and cemetery rules all change what is safe to do. If you are unsure at any point, stop — a stone can be cleaned again next month, but damage caused by the wrong method is permanent.