By Katherine Schlosser
For most of us, our garden tools are cleaned and stored, the holidays have passed, and we have a little more time to simply enjoy what we find in meadows, forests, fields, and even in our own backyards. Lichens can fill a part of the void we may be feeling. Their curious forms and means of growing and spreading, with which many of us are unfamiliar, can fill our minds with the wonders of things we normally pass without notice.
There are more than 5,000 species of lichen and lichen-dependent fungi in North America, with colors ranging from blues, lavender, yellow, red, orange, and gray to many beautiful greens. Color in lichens can depend on whether they are wet or dry. A major paint company even created a color they call Lichen to mimic the natural, earthy beauty of the organism. Perfectly described by Ed Yong in a July 2016 issue of The Atlantic, “They can look like flecks of peeling paint, or coralline branches, or dustings of powder, or lettuce-like fronds, or wriggling worms, or cups that a pixie might drink from.”
The forms lichens take are grouped in one of several general types, including:
Foliose – mostly flat with leaf-like structures, with each side having a different appearance
Fruticose – may have tiny “branches” and a bushy appearance
Crustose – appear like flat, crusty painted spots on trees, branches, logs, roof, or rocks
Other forms include:
Filamentous – stringy and hair-like
Gelatinous – jelly-like and somewhat formless
Leprose – have a powdery appearance
Squamulose – small, flat leafy scales with raised tips
Lichens have been used by humans for thousands of years, mostly as medicinals but also as foods, beverages, dyestuffs, cosmetics, brewing, animal fodder—even as an indicator of atmospheric pollution. As useful as they have been, our understanding of lichens has been slow.
Until the late 1800s, lichens were still thought of as plants. In 1868 Simon Schwendener, a Swiss botanist, identified them as a fungus and an alga living in a cooperative relationship. Later botanists recognized the relationship as mutually beneficial, with the alga using sunlight to produce nutrients and the fungus providing shelter, water, and minerals.
Botanists held with the partnership assumption, even though they struggled unsuccessfully to get lichens to grow in the lab. What they were missing was brought to light 150 years later by Tony Spribille, who spent years collecting lichen samples and screening them for genes of basidiomycete fungi.
What had been missed by generations of lichenologists was basidiomycetes, the third member in the partnership of lichens. With the right combination of two fungi and an algal species, a lichen would form. There is much more to learn, but thanks to Spribille, the journey has begun.
Quoting Ed Yong again, Spribille and his associates found that, through a microscope, “a lichen looks like a loaf of ciabatta: it has a stiff, dense crust surrounding a spongy, loose interior. The alga is embedded in the thick crust. The familiar ascomycete fungus is there too, but it branches inwards, creating the spongy interior. And the basidiomycetes? They’re in the outermost part of the crust, surrounding the other two partners. ‘They’re everywhere in that outer layer,’ says Spribille.” And the mystery was solved.
The most frequently noticed are the crustose lichens seen on trees, often looking like someone spray-painted blotches on tree trunks, or left a trail marker. These can vary from shades of gray to greens, blues, and yellows. They are attractive to me but lead some to think their tree has been attacked by disease.
No need to panic; these lichens don’t sink their “teeth” through the bark and into the tree. However, there are some lichens that contribute to the breakdown, or weathering, by physical and chemical processes, of the rocks to which they are attached. Physical effects occur by penetration of the rocks by hyphae and the swelling of organic and inorganic salts. Chemical processes include the “excretion of various organic acids, particularly oxalic acid, which can effectively dissolve minerals” (Chen 2000). The result is the eventual breakdown of rock into the mix of ingredients making our soil.
As an aside, Alexandra Rodrigues and associates inoculated newly created stained glass samples with fungi previously isolated and identified on original stained glass windows. They found that “fungi produced clear damage on all glass surfaces, present as spots and stains, fingerprints, biopitting, leaching and deposition of elements, and formation of biogenic crystals” (Rodrigues et al, 2014). Let that be a warning to keep your stained glass windows clean.
Of particular interest to members of The Herb Society of America are the useful aspects of these frequently overlooked species that are building blocks of our green planet. Found growing in moist, shady places, they also thrive in hot, dry lands. Though widely spread across the globe, growing on cold mountaintops to hot deserts on rocks, trees, fallen logs, on fertile soil or dry crust, each species has specific nutrient, air, water, light, and substrate requirements.
They vary widely in usability too, from serving as alerts for the presence of air pollution to providing survival food. Rock tripe, most often seen as green to black leafy-looking masses on boulders, might be the last thing you would consider putting into your mouth, but it turns out that, for thousands of years, they have saved people from starvation. After boiling and draining a few times, they can be made into a soup, even if barely palatable.
One of the more interesting lichens is known as Icelandic moss (Cetraria islandica ), which first came to my attention in the form of Fjallagrasa Icelandic Schnapps. If you look closely at the bottle pictured, you will see a sprig of the lichen in the bottle. Hand picked from the wilderness of Iceland, the lichen is steeped in alcohol, which extracts the color and flavor of the lichen. Sadly, I have not tasted it myself but have heard from a friend, and read, that it is a drink that requires a slight adjustment of expectations. Regardless, I’m almost willing to make the trip to Iceland just for the experience. The manufacturer recommends drinking “in moderation in the company of good friends”—a sound recommendation.
Beyond alcohol, this particular lichen has multiple medicinal uses, too. The active compounds in Icelandic moss have demonstrated antioxidant, antibacterial, and antifungal properties (Grujicˇic´ et al., 2014).The mucilaginous compounds (polysaccharides) aid in soothing oral and pharyngeal membranes, relieving coughs of common colds.
Scandinavian countries were long known to use Icelandic moss in making breads and soups. They dried the moss, reconstituted it, then dried it again and ground it to mix into flour. Due to the polysaccharides, the lichen added structure as well as flavor. Many other cultures used it as an addition to flour to cut the expense of flour. Used far less now, over the years, it was an important source of nutrients for many people.
Parmotrema perlatum, commonly known as black stone flower, is used as a spice in India and elsewhere, and is often added to Garam Masala blends. As found, it has no fragrance; exposed to the heat of cooking, it releases an earthy, smoky aroma.
Unlikely as it sounds, some lichens can be fragrant, and some act as a fixative in the preparation of cosmetics and perfumes. Oakmoss lichen, used in perfumery, is found on oak trees, as well as a few other deciduous trees and pines.
A number of lichens are used in the dyeing and tanning industries. If you took high school science, you are familiar with Litmus strips. Those strips are made from litmus, which is obtained from a couple of species of lichens, Roccella tinctoria and Lasallia pustulata.
Winter may be upon us, but there is still plenty to see and study right under our noses in the garden, yard, and out walking on trails. Take notes, take photos, and spend a lazy afternoon identifying what you have found and what uses it may have. Future ventures into the forest will hold considerably more interest for you.
Medicinal Disclaimer: It is the policy of The Herb Society of America, Inc. not to advise or recommend herbs for medicinal or health use. This information is intended for educational purposes only and should not be considered as a recommendation or an endorsement of any particular medical or health treatment. Please consult a health care provider before pursuing any herbal treatments.
Photo Credits: 1) Old man’s beard (Usnea articulate), a fruticose lichen, photo taken in Linville Falls, NC 2009 (Kathy Schlosser); 2) Lobaria pulmonaria, tree lungwort, used for its astringent properties in tanning, photo taken in Acadia National Park, 2014 (Kathy Schlosser); 3) A foliose rough speckled shield lichen (Punctelia rudecta) covered with isidia (tiny projections which can detach to form new growth and grow from the white spots and streaks), photo taken on the Blue Ridge Parkway, NC 2009 (Kathy Schlosser); 4) Umbilicaria mammulata, smooth rock tripe (Alex Graeff, iNaturalist); 5) A crustose lichen species in Acadia National Park, 2014 (Kathy Schlosser); 6) Pixie cups lichen (Cladonia sp.) growing amongst a cushion moss (Dricanum sp.), 2011 (Kathy Schlosser); 7) Cetraria islandica, Iceland moss (Darya masalova, iNaturalist); 8) Parmotrema caperata (now P. perlatum) as it appears in Flora Batava, vol. 10, 1849 (via Wikimedia); 9) Evernia prunastri, oakmoss lichen used in perfumery (Liondelyon, via Wikimedia)
Adams, Ian. Shield lichens at West Woods, Geauga County. Ian Adams Photography website, March 29, 2020. https://ianadamsphotography.com/news/shield-lichens-at-west-woods-geauga-county/ Accessed 12-04-2021.
Cetraria islandica, Iceland moss. https://pfaf.org/user/Plant.aspx?LatinName=Cetraria+islandica Accessed 12-15-2021.
Chen, J., H-P. Blume, and L. Beyer. 2000. Weathering of rocks induced by lichen colonization: A review. CATENA. 39(2). https://doi.org/10.1016/S0341-8162(99)00085-5. https://www.sciencedirect.com/science/article/pii/S0341816299000855 Accessed 12-19-2021.
Crawford, S. D. 2015. Lichens used in traditional medicine. Lichen Secondary Metabolites, chapter 2. Springer International Publishing. DOI: 10.1007/978-3-319-13374-4_2 Accessed 12-28-2021
Daniel, G., and N. Polanin. 2013. Tree-dwelling lichens. Rutgers, N.J. Agricultural Experiment Station. https://njaes.rutgers.edu/fs1205/ Accessed 1-1-2022.
Fink, B. 1906. Lichens: Their economic role. The Plant World. 9(11). Published by Wiley on behalf of the Ecological Society of America. Stable URL:
https://www.jstor.org/stable/43476359 Accessed 11-18-2021.
Graeff, Alex. Smooth Rock Tripe, Umbilicaria mammulata. Photo 70633379, iNaturalists, (some rights reserved (CC BY-NC-ND). https://www.inaturalist.org/photos/70633379 Accessed 12-29-2021.
Grujičić, D., I. Stošić, M. Kosanić, T. Stanojković, B. Ranković, and O. Milošević-Djordjević. 2014. Evaluation of in vitro antioxidant, antimicrobial, genotoxic and anticancer activities of lichen Cetraria islandica. Cytotechnology. 66(5): 803-813.
Kops, Jan. Flora Batava of Afbeelding en Beschrijving van Nederlandsche Gewassen, (1849). Parmelia caperata, illus. Christiaan Seep, Vol. X, Amsterdam, Deel. https://commons.wikimedia.org/wiki/File:Parmelia_caperata_%E2%80%94_Flora_Batava_%E2%80%94_Volume_v10.jpg Accessed 11-09-2021.
Lichen Identification Guide, Discover Life website. https://www.discoverlife.org/mp/20q?guide=Lichens_USGA Accessed 1-1-2022.
Max Planck Society. The hidden talents of mosses and lichens. https://phys.org/news/2021-12-hidden-talents-mosses-lichens.html
Perez-Llano, G. A. 1944. Lichens: Their biological and economic significance. Botanical Review. 10(1). Stable URL: https://www.jstor.org/stable/4353298 Accessed 12-23-2021.
Perez-Llano, G. S. 1948. Economic uses of lichens. Economic Botany. 2: 15-45.
Rodrigues, A., S. Gutierrez-Patricio, A. Zélia Miller, C. Saiz-Jimenez, R. Wiley, D. Nunes, M. Vilarigues, and M. F. Macedo. 2014. Fungal biodeterioration of stained-glass windows. International Biodeterioration & Biodegradation. 90. https://doi.org/10.1016/j.ibiod.2014.03.007. https://www.sciencedirect.com/science/article/pii/S0964830514000663 Accessed 12-19-2021.
U.S. Department of Agriculture, U./S. Forest Service, Lichens Glossary. https://www.fs.fed.us/wildflowers/beauty/lichens/glossary.shtml Accessed 12-04-2021.
U.S. Department of Agriculture, U.S. Forest Service. Lichen Habitat. https://www.fs.fed.us/wildflowers/beauty/lichens/habitat.shtml Accessed 12-18-2021.
U.S. Department of the Interior, National Park Service. Lichens—The Little Things That Matter https://www.nps.gov/articles/lichen-and-our-air.htm Accessed 12-21-2021.
Yong, E. 2016. How a guy from a Montana trailer park overturned 150 years of biology. The Atlantic, July 22, 2016. http://www.theatlantic.com/science/archive/2016/07/how-a-guy-from-a-montana-trailer-park-upturned-150-years-of-biology/491702/ Accessed October 2016.
Katherine Schlosser (Kathy) has been a member of the North Carolina Unit of The Herb Society of America since 1991, serving in many capacities at the local and national level, including as a member of the Native Herb Conservation Committee, The Herb Society of America. She was awarded the Gertrude B. Foster Award for Excellence in Herbal Literature and the Helen de Conway Little Medal of Honor. She is an author, lecturer, and native herb conservation enthusiast eager to engage others in the study and protection of our native herbs.