About that dying red maple tree covered with lichen in our front yard...you should know that it was disease--not the lichen--that harmed the tree. With that in mind, if you have a dying tree in your yard, what would you do with it? Before you shout, "Cut it down!" read on about lichens, an ecosystem wonder.

What are Lichens?

The University of California Museum of Palentology's website describes lichen as, "... symbiotic associations of two different organisms..." The organisms referred to are fungus and alga. The protection and structural support offered by the fungus, and the food from photosynthesis by the algae, result in a working symbiotic relationship between the two.

Foliose lichen on dying red maple treeLichens grow in terrestrial (land) or aquatic landscapes around the world. These diverse organisms can be found in areas of weather extremes, from atop hot sunny mountain rocks to substrates of tree bark, rocks, watersheds, soil and leaves.

Important and fascinating, lichens are studied around the world by lichenologists, environmentalists, biologists, and science students. Robert S. Egan, from the Department of Biology at the University of Nebraska in Omaha, has documented over 200 professional articles written just in the past year about lichen.[1] His published literature includes everything about lichens, from newly discovered species to composition and morphology.

Lichen Uses
Lichens have been used and valued by both people and wildlife for centuries. They generally grow best in non-polluted areas. Photo by Barbara Page: Foliose lichens on rock

Lichens and People

Beatrix Potter, best remembered for childrens' books such as Peter Rabbit, spent time studying and drawing lichens. Her illustrations offer detailed and accurate renditions of their delicate beauty.[2]

Throughout history native cultures and traditions have found practical uses for lichens. Native Americans in New Mexico collect Xanthoparmelia chlorochroa for use in dye to color yarns and fabric.[3] Usnic acid, derived mainly from Usnea sp. lichens, is used in other countries in antibacterial and antifungal alternative medicines; and is used in the U.S. in perfumes, botanical supplements, toothpaste and in other commercial products, such as Tom's of Maine natural deodorant sticks.

Lichens and Wildlife

Lichens benefit ecosystems and wildlife, offering moisture and humidity by their ability to retain water. They also serve as a refuge from predators for amphibians and insects, who hide and lay eggs in lichen.

Many species of birds in North America use lichens. The spruce grouse and wild turkey eat lichen. Warblers and Vireos use lichens in their nests, and Photos by: DG member 'sunnyg'Golden plovers use Thamnolia vermicularis in their nests. The olive-headed weaver in Madagascar makes its nests solely from lichen in the genus Usnea.[4] I've never had the pleasure of seeing a hummingbird nest in person, but Dave's Garden (DG) member 'sunnyg' of San Jose, CA, had the experience (see photos). A closeup look shows Hummingbirds may include soft thistle and dandelion seed fluff, along with expandable, stretchy spider silk and leafy materials in their nest. They may add a dab or two of pine resin as 'glue' before a final layering of lichens around the outside of their nest for lightweight insulation and camouflage.[5]

Cows, antelope, deer, elk and small mammals also utilize lichen. Mountain goats in southeastern Alaska include Lobaria linita in their diet; northern flying squirrels use lichen Bryoria fremontii as nesting material and food. The primary diet of the endangered Yunnan snub-nosed monkey, consists of two species of Bryoria. And during the winter season, Caribou use their keen sense of smell to find a good feeding area with lichen beneath snow.[6] Photos by Stephen & Sylvia Sharnoff

Lichens and Pollution

Lichens are extremely vulnerable to habitat alteration. It comes as no surprise then, that the habitats with the highest lichen species diversity are remnants of ancient forests and other undisturbed ecosystems. The association between a large diversity of lichens and unpolluted habitats is so evident, scientists use lichens as indicators of ecosystem continuity to help identify areas that should be protected.

The bark of red alder trees is usually covered by white lichens. When these trees are in a polluted environment, lichen cannot grow (see photos).

Types of Lichen

There are thousands of lichen species in the United States and Canada, with 2,650 alone found in U.S. National Parks.[7] My first experience with lichens was while hiking in the Adirondack Mountains in New York with my husband, Harry. We enjoy Photo by Diana Wind: Adirondack Mountains, NYour mountain hikes, exploring nature's beauty and wonders and often see lichen growing on tree trunks, fallen limbs and on the surface of mountain rocks. The photo shown was taken atop one of our climbs. In some areas, on trails and summits, signs are posted asking hikers to please be respectful and not touch or disturb the fragile growing lichens.

DG member 'PotEmUp' of Fremont, California remembers Staghorn Lichen (Wolf Lichen, Letharia vulpine) "as one of the beautiful things that I grew up with." When lichen is observed up close or under magnification, its unique and beautiful form can really be appreciated.

DG member 'Kelli' from the west coast in Canoga, California shared her photos of tree lichen on Monterey pines Photos by DG member 'kelli': Ramalina menziesii(shown) saying, "If there are magical places, this has got to be one of them. "The lichen in her photos is Ramalina menziesii (Lace lichen), with possibly some Usnea," according to lichen expert, Stephen Sharnoff. Although it is not a moss, Ramalina is often called California Spanish moss. Lace lichen is common on the west coast of North America.

How can you tell Lichen apart?

Lichens can be differentiated by examining their surface texture, color and lobules. Textures can be granular, smooth or veined, and colors vary from white or grey to interesting orange, reds, yellow-greens and greens. Lobules, the growths coming out from the lichen, are used in the lichen's reproductive process.

With so many types of lichen, identifying the genus and species can be quite challenging. Experts have various ways to determine them. Naturalist Jim Conrad suggests that backyard gardeners recognize three types of lichen: Crustose, Foliose and Fruticose.

Crustose Foliose Fruticose
Like the powdery white flat lichen seen on mountain rocks
Like those shown below
Actually look like little shrubs

Photos by DG member 'threegardeners' - identification unknown

Photo 1) Foliose-possibly a species of Physcia

Photo 2) large leafy Foliose-possibly Parmelia sulcata; Shrub-like-possibly Anaptychia

Photo by DG member 'PotEmUp'

Shrub-like-Staghorn Lichen, found near

Donner Summit off highway 80 in CA

Crustose lichens look flat and white--like chalk drawn on the rocks--and grow on the rock like a crust.Photo by DG member 'bonitin': Maritime lichen Foliose may appear similar in its young growth, but as it ages the edges curl up. Fruticose are shrub-like and, as the name suggests, resemble little shrubs.

The foliose specimen, 'Maritime Sunburst Lichen', Xanthoria parietina is in the Teloschistaceae family, commonly found on the northeast coast and is yellow-orange, orange, yellow-green in color. This beautiful lichen inspired my lichen recipe below.

Earth Day Recipe

Note: Lichens should NOT be eaten by people because some are poisonous. The average person would not be able to determine safe lichen from unsafe, similar to mushrooms, so never try to eat real lichen.

Enjoy this fun, crispy almond tuile cookie recipe that reminds me of lichen with its thin and curvy shape.

Diana's Maritime TuilesDiana's Maritime Tuiles ~
Lichen, look-a-like, wafer cookies

Tuile (pronounced "twheel") cookies are usually molded to a curved shape by draping the hot, thin, cooked cookie over a rolling pin, baguette pan, bowl, or other curved object while it cools. Tuile is French for "tile", and as the name implies, the cookies resemble roofing tiles. Classic tuiles are traditionally made with almonds.Creative versions include chocolate, vanilla or various flavors with or without nuts, herbs or other additions.

Tuiles are delicious on their own as a light cookie or as a garnish to low-fat frozen yogurt or sorbet. The thin batter can be transformed into ribbons, leaves, butterflies, whatever creative stencil you would like. Stencils can be cut out of plastic lids or clean unused manilla file folders or poster paper. The batter is then spread over top of the stencil using your fingers or a palette knife. And when the stencil is lifted off - the shape is easily formed. The batter has to be just the right consistency for it to work and hold the shape. It can easily be thickened if necessary by adding a bit more flour, or thinned by adding a bit more egg white. Humidity is a factor, tuiles should not be attempted in high humidity or they will lose their crispness quickly. Best stored in an airtight container.Making Diana's Maritime Tuiles

Yields six 5-inch or one dozen 3-inch tuiles


2 tablespoons no-salt butter

1/3 cup sugar

1/2 teaspoon grated orange peel

1/4 teaspoon almond extract (or 1/8 teaspoon almond oil flavor)

2 large egg whites

1/3 cup unbleached, all-purpose flour

1/2 cup toasted sliced almonds

optional: food color (green)

1) Optional: Make a circle shape stencil. Keep the diameter 5 inches or less so it's manageable. Trace something in the size you would like, then cut out the inside. Cut around your shape, leaving a one inch border. Lichens are all shapes so a stencil is not really necessary, but it can give you stencil practice if you ever want to try a butterfly or something fancier in the future.

2) Spray baking pan with non-stick spray or use a non-stick, silicon mat (nonstick mats do not require any spray). Set aside.

3) Cream butter and sugar until light. Add orange peel and extract. Beat in egg whites. Mix in flour then stir in 2 tablespoons of the almonds, reserving the remaining almonds to sprinkle on top of the batter. Add food color if desired.

4) Place your stencil on the prepared pan and spoon on batter in the center of the stencil. Using a small palette knife or your fingers, smear the batter thin and uniform to the edges of the stencil. These are fun to make, reminiscent of finger painting. A little batter goes a long way. Remove the stencil and repeat. Sprinkle a few almonds on the top. Consider the first few as trials until you get the hang of it. If the batter is spread too thick, they will be chewy and if too thin, they will be too delicate.

5) Bake at 400°F 3 to 4 minutes or until edges and into center start to turn golden brown. Remove tray from oven. Remove tuiles quickly from the baking sheet (be careful they are hot) and drape them over a rolling pin, baquette pan or bowl. Allow to cool and harden before removing.

6) Store tuiles in airtight container until ready to serve.

Nutrition Analysis: Serving size one 5-inch tuile: 103 calories (5%DV), total carbohydrate12.1 g (4%DV), dietary fiber .7 g (3%DV) , total fat 5.3 g (8%DV), saturated fat 1.8g (9%DV), protein 2.5g (5%DV), vitamin A 78.7IU (2%DV), calcium 13.7mg (1%DV), potassium 54.7mg (2%DV), sodium 14.1mg (1%DV), cholesterol 6.7mg (2%DV).

Note: Percent Daily Value (%DV) is a percentage (based on a 2,000 calorie daily diet) as a frame of reference to tell if a serving of food is high or low in a nutrient. It is used on food nutrition facts labels.

Photo by DG member 'Margiempv': Iris LichenCheck out Iris ‘Lichen'. No relation to lichen, but aptly named as such, with its sultry appeal and curvy beard.

Photo credits: Red Alder photographs used with permission © 2009 copyright Stephen and Sylvia Sharnoff, All rights reserved. Adirondack Mountains, Recipe photos, Thumbnail: ©2009 Wind (Lichen image Wikipedia, public domain. The 83rd plate from Ernst Haeckel's Kunstformen der Natur 1904 - Globe clip art: http://www.freeclipartnow.com/geography/earth/). Foliose lichen on rock by Barbara Page, GNU Free Documentation License, Wikipedia. Photos from DG members ©2009 by respective parties: Staghorn lichen by 'PotEmUp', Ramalina menziesii by 'Kelli', Hummingvirs nests by 'sunnyg', Parmelia sulcata and Anaptychia by 'threegardeners', Maritime Sunburst lichen by 'bonitin', Iris Lichen by 'Margiempv'.

Special thanks to all Dave's Garden contributors and to the Sharnoffs

Happy Anniversary! to Linda and Russell and to all happy couples who chose Earth Day as their special wedding day.


[1] Egan R., The Bryologist. March 1, 2009, vol 112; p 239

[2] Introduction to Lichens, an alliance between kingdoms. University of California Museum of Palentology. Accessed April 1, 2009.

[3] Sharnoff S., Lichens Uses by People: Dyeing. Accessed April 8, 2009.

[5] Pranis E, Hummingbird Journey North, Building a Hummingbird Nest - Strong, Soft, and Stretchy. Accessed April 19, 2009.

[4] [6] Lichens of North America. Wildlife. Accessed April 8, 2009.

[7] National Biological Information Infrastructure, NPLichen, A Database of Lichens in the U. S. National Parks. 2009; Version 4.5. U. S. Geological Survey

Further Reading: Honor Earth Day with a Family Hike by Sally G. Miller

Spanish Moss - Adding that Southern Touch, and More! By LariAnn Garner (Spanish Moss is similar to lichen, but it's not)

Related Books: Dave's Garden Bookworm lists 4 books on lichen, including: Lichens of North America, by Irwin M.Brodo and the Sharnoffs, published 2001 by Yale University Press.You can order Lichens of North America directly from Yale University Press.

Related Links:

The California Lichen Society

Lichenland Fun with lichens by Oregon State University

Arizona State University Lichen Herbarium

Lichens Specimens and Natural History by Stephen and Sylvia Sharnoff

Lichen use by wildlife in North America by Stephen Sharnoff and Roger Rosentreter (Bureau of Land Management, Idaho)

Backyard Nature, Lichens, with naturalist Jim Conrad

Celebrate Earth Day, April 22nd Earth Day Network

Pinnacles National Monument - California Lichen Society