Look closerFungi
Lichens on gravestones and old stone walls
When: All year
The gray, yellow-green and orange crusts on old gravestones and stone walls are lichens, each one a fungus living in partnership with an alga. Many grow slowly, so a large patch can be very old, and different kinds of stone tend to carry different lichens.
Why this time of year
Lichens stay on the stone all year, drying out in dry spells and reviving after rain, so any snow-free day works for a close look at an old stone wall or burying ground.
How to notice it
- Stay on the paths and keep your hands in your pockets. Look at a stone or wall from a step or two away first, then lean in with your eyes only.
- Pick out the colors: flat gray or pale green crusts, bright yellow-green patches, and orange circles. Notice how many patches spread outward in rounded or circular shapes.
- Compare two stones made of different rock, such as dark slate and pale marble or speckled granite. See whether the crusts differ in color, size or shape.
- Find the biggest patch you can and look at the date carved nearby, if there is one. A slow-growing lichen may have been spreading there for much of that time.
Try this with kids: Be a stone detective from a respectful distance: count how many different lichen colors you can spot, and tell a grown-up which stone has the biggest patch. Eyes only, no touching.
Word to know: A “lichen” is a fungus and an alga (or cyanobacterium) living together as one organism.
Safety
- Never scrape, pick or clean lichens or stones. Old stones can be fragile and cleaning can damage them.
- Stay on paths, do not lean on or touch markers, and leave any leaning or cracked stone alone.
Sources
- fs.usda.govUS Forest Service. Lichen = symbiotic partnership of a fungus and an alga; alga may be green or blue-green (cyanobacteria); lichens colour rocks and cliffs, crust forms. Quote: 'a symbiotic partnership of two separate organisms, a fungus and an alga.' Refute pass also read: the alga can be 'a green alga or a blue-green alga, otherwise known as cyanobacteria'; lichens survive dry spells 'as long as there are occasional rain showers or flooding to let them recharge'.
- britishlichensociety.org.ukBritish Lichen Society (learned society). Churchyards hold many rock types 'each having their distinctive lichen communities'; some lichens grow 'sometimes less than half a millimetre a year'; long-lived individuals may be 'almost as old as the gravestones upon which they live'; scrubbing a gravestone loses lichens with the weathered surface. UK source, applied here only as general biology. Refute pass also read: 'Some species grow very slowly, sometimes less than half a millimetre a year' while others grow faster; some take 'hundreds of years' to become established; 'golden circles of Caloplaca' on limestone.
- britishlichensociety.org.ukBritish Lichen Society. Record the stone type (granite, sandstone, limestone) because it links to lichen distribution; 'calcareous stone surfaces may buffer species from the acidity of pollutants'; some lichens live very long.
- nps.govNational Park Service Preservation Brief 48 (PDF). 'Microorganisms such as algae, fungi, and lichens may affect grave markers'; with acid-sensitive limestone and marble 'the result is surface erosion'. Cleaning: 'the use of improper materials and techniques can cause great damage'; 'first do no harm'; 'chemical cleaning can accelerate deterioration'. Cleaning is for trained staff. Notes slate markers exist.
- resources.culturalheritage.orgAmerican Institute for Conservation blog (Maine seminar). Quote: 'Different lichen species grow on different stone types in different environments.' Grave markers of granite, marble, slate and sandstone host lichens and biofilms.
Checked against these sources on October 30, 2026.