Lichens growth, cleaning & prevention on stone surfaces:

This article describes and provide photographs and advice on identifying, cleaning, and preventing lichens growth on stone surfaces such as buildings, cultural artifacts, statues, gravestones, sidewalks, stone walls, and pictographs. We include links to references useful in the identification of algae, moss, lichens, and mold.

Appearance of Lichens on Stone Surfaces

Colors & Types of Lichens Growth Stone, Marble, Masonry, Tile or Slate Surfaces

We discuss the cleaning/restoration of lichens and moss covered stone surfaces such as building components,cultural artifacts, and grave markers and lichens removal in more detail at Methods for Cleaning Stone Surfaces.

Once we include lichens (such as our photo at left, from Portland Maine), the range of colored growths or stains on stone surfaces is quite large. But the most common stain colors are

• Black (or dark brown) - most often due to algae, bacteria, dirt or soot, fungus. Fungus may also on occasion produce green or white films on stonework. [Photo of black-brown roof algae On antique metal roof shingles]
• Brown or red rust stains - occur on masonry usually due to combination of water and metal components
• Green - most often due to algae or moss
• Light green, yellow, red, gray, white - most often due to lichens.

Below we provide example photographs of different colors and sources of stain or contaminants on stone or masonry surfaces, followed by advice on cleaning and stain prevention.

Also see our Catalog of Biological Substances that Alter Stone or Other Inorganic Materials, and see ALGAE, FUNGUS, LICHENS, MOSS COMPARED for a comparison of algae, fungus, lichens, or moss on other building surfaces such as roof shingles.

Reindeer moss: Our second moss and lichens photo (above right, Quetico boundary canoe area, Canada) demonstrates that moss and lichens can coexist happily on the same surface, and even intermixed on a surface where we show two kinds of moss. In our photo, the taller pale growth among the green moss is itself "Reindeer Moss, Caribou Moss" or in other references "Antler Moss".

Our photograph shows Cladonia rangeferina or perhaps Cladonia sp. along with both moss and other lichens on the same stone. Reindeer moss is itself actually a lichen, and is an important food source for reindeer and caribou). Reindeer moss is quite fragile and slow growing, found in both hot and cold climates and in alpine tundra - don't trample it in the wild.

Lichens, one of the most hardy growth organisms found in nature, can grow in harsh conditions. Moss and lichens are both more than a cosmetic issue on most materials.

By holding moisture against the stone or other material surface lichens but more so moss speed the wear of the surface in freezing climates by increasing frost damage to the surface and by action of the organism's "roots" that penetrate the material surface.

Our photo (left) shows green lichens growth on a gravestone near Vassar College, in Poughkeepsie, NY. Notice that the lichens appears first on the more roughened stone surfaces inside the carved gravestone lettering, and on the rough-cut north face of the stone.

In addition to stone surfaces and mineral-covered roof surfaces, lichens also grows just fine on clay tile roofing and on wood (as those photo links show).

The lichens shown on the stone monument (above left), and the flat black stone (above right), demonstrate that this organism is happy in an enormous range of climates, from high elevation hot dry southern areas (Las Cabras, Guanajuato, Mexico, at about 7000' elevation) to arctic tundra (above right, elevation 50', in Northern Norway near Kirkenes [(Finnish: Kirkkoniemi, Sámi: Girkonjárga) the centre of the municipality of Sør-Varanger in Finnmark county, Norway], well above the arctic circle, courtesy Jennifer Church).

White Lichens photos: White & Pale Gray Lichens photos: The importance of lichens as an organism that can attack cultural artifacts is demonstrated by our photo (left) of lichens surrounding a pictograph from the Quetico boundary waters canoe area in Canada. Also see our pale lichens photos just above in this article. Also see these photos of gray-green roof lichens and gray roof lichens.

For more about conservation of stone artifacts such as this pictograph, consult "Microbial Communities in Caves: Ecology, Physiology, and Effects on Paleolithic Paintings" found in Art, Biology, and Conservation: Biodeterioration in Works of Art, Robert J. Koestler et als. Eds., Metropolitan Museum of Art, 2003, ISBN 1-58839-107-8, p. 210-225.

Green Lichens photos: See Green Stains on Stone for additional green lichens pictures - our photo of "Reindeer Moss, Caribou Moss" or in other references "Antler Moss". Our photograph shows Cladonia rangeferina or perhaps Cladonia sp. along with both moss and other lichens on the same stone.

Yellow Lichens photos: see Colors & Stains on Stone for our photo of yellow-orange lichens on stone.

Lichens on Roofs demonstrate the mechanical damage that can be caused by lichens on surfaces.

See LICHENS on ROOFS for details about the causes, effects, and prevention of lichens growth on roofing surfaces. Lichens is often found growing on roof shingles, especially asphalt and wood shingles as we show here where we demonstrate the damage to the surface when lichens is removed. Our photos (below) illustrate how serious lichens damage can be to a mineral surface.

Does Lichens Always Need to be Cleaned Off of Stone Surfaces?

No, of course not. The lichens growing on this stone wall in Poughkeepsie, NY (constructed by and found at Adams Fairacre Farms) is not going to do any harm, and in fact adds to the attractiveness of the wall.

Also see Lichens on Roofs for a discussion of lichen damage to shingles and how to prevent lichens growth on roofs.

This website tells readers how to identify, evaluate, remove or prevent stains on building surfaces.

Resistance of Stone Surfaces to Lichens, Moss, Algae

Reader Question:

4/21/2015 martin rowe said:
which stone is best for resisting lichens, algae & mosses?

Reply:

Martin,

Based on what I've seen of stone surfaces around the world and under lichens, algae and moss friendly conditions (cool, wet, shaded), stones with a hard-finished surface such as polished granite are more resistant to those organisms, principally because of the water-shedding property of the surface and perhaps secondarily because the smoother surface also allows spores to wash away.

Take a look at the gravestone at page top. I've seen this pattern quite often: moss is growing in the cut-out letters where the stone surface is smooth (and less vertical). You'll notice that the very mossy left side of this stone was left rough-cut.

For the guys who know, see

• Griffin, P. S., N. Indictor, and R. J. Koestler. "The biodeterioration of stone: a review of deterioration mechanisms, conservation case histories, and treatment." International Biodeterioration 28, no. 1 (1991): 187-207.
• Li, Gary, and Athol D. Abrahams. "Controls of sediment transport capacity in laminar interrill flow on stone‐covered surfaces." Water resources research 35, no. 1 (1999): 305-310.
• Lisci, Marcello, Michela Monte, and Ettore Pacini. "Lichens and higher plants on stone: a review." International biodeterioration & biodegradation 51, no. 1 (2003): 1-17.
• De los Rios, Asunción, and Carmen Ascaso. "Contributions of in situ microscopy to the current understanding of stone biodeterioration." International Microbiology 8, no. 3 (2005): 181.
• Tretiach, Mauro, Stefano Bertuzzi, and Fabio Candotto Carniel. "Heat shock treatments: a new safe approach against lichen growth on outdoor stone surfaces." Environmental science & technology 46, no. 12 (2012): 6851-6859.
• Scheerer, Stefanie, Otto Ortega‐Morales, and Christine Gaylarde. "Microbial deterioration of stone monuments—an updated overview." Advances in applied microbiology 66 (2009): 97-139.
  

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Continue reading at STONE, STUCCO & BRICK CLEANING METHODS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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LICHENS on STONE SURFACES at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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Citations & References

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