If you do any hiking in Nova Scotia, New Brunswick, Ontario, or British Coumbia’s forests, you’ve likely come across tree lungwort (Lobaria pulmonaria). Tree lungwort is widely distributed across the Northern Hemisphere.1 Its bright green colour and distinct lung-like appearance make it easy to recognize. Here, in the Maritimes, there is no other lichen or plant that resembles it.2
Recently, I ventured into the forest near my home in search of L. pulmonaria. It didn’t take long to find some. Its presence denotes a healthy ecosystem with little air pollution or acid rain. Below, you’ll find more information about this lichen, the role it plays in the ecosystem, and its cultural and medicinal significance for humans. Next time you are out in the woods, take a look around and see if you can spot this curious lichen.
What Are Lichens?
Lichen is a composite organism formed from fungus and a photosynthetic partner, either green alga or cynobacteria.5 About one-fifth of all fungi are lichenized and it’s estimated that 6% of the Earth’s land surface is covered by them.3 You’ll find lichen growing on trees, rocks, houses, cement, plastic, glass, and metal – basically any undisturbed surface.4 Lichen can grow almost anywhere because they derive all their nutrients from the air, rain, and sun.
Normally, a fungus lacks chlorophyll to derive energy from the sun, but when it associates with an alga or cyanobacteria it gains access to photosynthesis.6 When cynobacteria is present, lichen also has the ability to convert atmospheric nitrogen into ammonia for nutrition.6 In return, the fungus provides a protective home for the alga and/or cynobacteria.6 This type of mutualism is called a symbiotic relationship.
Tree lungwort contains both alga and cynobacteria. The alga lives in the top layer of the thallus (lichen body) and the cyanobacteria lives in the lower layer.8
Identifying Tree Lungwort
As its name suggests, tree lungwort resembles lung tissue with its many ridges, depressions, and lobes. When it’s well hydrated, you might also argue, it looks like a big salad. Foliose lichens, like L. pulmonaria, are large and leafy with distinctive tops and bottoms. In wet conditions, tree lungwort is a bright green colour with a pale cream or orange underside. In hot and dry conditions, the lichen is a grey or dull brown colour.
Tree lungwort can produce reddish-brown apothecia. Apothecia are the fruiting/spore producing bodies of the fungal partner.9 However, L. pulmonaria usually reproduces asexually by breaking off and establishing itself elsewhere as a new individual.9
L. pulmonaria can grow in huge clumps – sometimes the length of an entire tree! Because it derives nutrition from the atmosphere, it never harms the trees it grows on. You can find smaller patches of tree lungwort growing on rocks.
Generally, L. pulmonaria prefers to grow in partially shaded areas, though it can be found in sunny and dark-shaded places.7 On the west coast of Canada and in Europe, it is most often associated with old growth forests.9 Here in the Maritimes, I’ve found it in younger forests. That said, tree lungwort only grows a few millimetres per year, so you’ll be hard pressed to find large amounts in young forests.
Tree Lungwort in the Ecosystem
L. pulmonaria plays an important role in the ecosystem as a nitrogen fixer and a source of food for animals. Its sensitivity to pollution make it a useful bioindicator to help screen the health of an ecosystem.
Cyanobacteria living within tree lungwort convert nitrogen into nutrients that are readily available for use by other plants and animals.8 When L. pulmonaria falls to the ground and decomposes, this converted nitrogen is released into the soil. As a result, there is a constant drip of nitrogen down from the forest canopy where it grows.11 This nitrogen cycling is important because many forest ecosystems lack abundant nitrogen sources.10
Scientists have demonstrated that lichens, like tree lungwort, are strong bioindicators of climate, air quality, acid rain levels, and habitat health.3 Because lichens are specially adapted to receive their nutrients from the atmosphere, they are especially sensitive to the effects of air pollution. When exposed to air around industrial areas, many lichens will slowly disintegrate and die.3 A lichen rich forest is a sign of good air quality.
Food and Nest for Animals
In addition to being important nitrogen fixers, tree lungwort is also a source of food for deer, moose, and insects.12 It is also used as nesting materials by birds and chipmunks.12
Uses for Tree Lungwort
Tree lungwort has been used as a folk medicine and a fabric dye. If you use it, it’s important to harvest with care.
L. pulmonaria has long been used as a traditional medicine in teas and tinctures. Some claim that its resemblance to lung tissue provides a clue to its potential as a remedy for respiratory issues like asthma, pneumonia, and tuberculosis. I can find no good evidence for this, but science has backed L. pulmonaria as being anti-inflammatory and useful in preventing ulcers in rats.13 There is also promising research that it may be useful as a preventative for Alzheimer’s disease, but more research is needed.14
The Coast Salish people used tree lungwort as a dye for wool.15 By boiling the lichen in water for a couple of hours, you can make an orange/tan dye. For detailed instructions check out this YouTube video.
Because of its role in the forest ecosystem, it’s important to harvest tree lungwort sparingly. L. pulmonaria only grows a few millimetres per year. Taking even a small amount could be harvesting years and years of growth. When harvesting for dyestuff, it is best to collect “specimens from a disturbed area such as a recent logging operation, or from wind fallen trees.”3
Other Articles You May Enjoy
1 Hallett. 2019. “Indigenous Uses of Native Plants.” Connecting Albert County.
2 Brodo, Cameron, Andrachuk, and Craig. 2001. “Identifying Nova Scotia Lichen.” Environment Canada.
3 McCoy. 2016. Radical Mycology: A Treatise on Seeing and Working With Fungi. Chthaeus Press.
4 Machesney. 2020. “Lichen in the Garden.” PennState Extension.
5 Piganeau and Coleman-Derr. 2016. “Understanding Microbial Multi-Species Symbioses.” Frontiers in Microbiology.
6 Vidyasagar. 2021. “What Are Lichens?” Live Science.
7 Schiefelbein and Thell. 2018. “Current state of Lobaria pulmonaria in southernmost Sweden.” The Nordic Lichen Society.
8 Rolih. 2018. “Tree Lungwort.” National Park Service.
9 Galloway. 2015. “Lungwort.” Mountain Lake Biological Station: University of Virginia.
10 Norby and Sigal. 1989. “Nitrogen Fixation in the Lichen Lobaria pulmonaria in Elevated Atmospheric Carbon Dioxide.” Oecologia.
11 Pallotta. 2021. “How to Harvest and Process Lungwort with Michael Pilarski.” Friends of the Trees Botanicals.
12 DeLay. “Plant of the Week: Lungwort, Lung Lichen.” US Forest Service.
13 Süleyman et. al. 2003. “Anti-inflammatory and antiulcerogenic effects of the aqueous extract of Lobaria pulmonaria (L.) Hoffm.” Phytomedicine.
14 Pejin, et.al. 2012. “A New Depsidone of Lobaria pulmonaria with Acetylcholinesterase Inhibition Activity.” Journal for Enzyme Inhibition and Medical Chemistry.
15 Heather. 2014. “Lichen Dying.” True Stitches.