Woolly Foam

(Stereocaulon tomentosum)

Conservation  •  Description  •  Ecology  •  Distribution  •  Taxonomy

Woolly Foam - Featured photo
Photo by Dan W. Andree

Conservation Status

IUCN Red List

not listed

NatureServe

NNR - Unranked
SNR - Unranked

Minnesota

not listed

Description

Woolly Foam is a common and widespread shrubby lichen. It occurs in Europe, Asia, North America, and South America. In the United States it occurs in the east from Maine to Connecticut, west to Minnesota, and in the west in Washington State and Oregon. It grows on the ground or among mosses, rarely on rocks, forming a loose, mat of widely spreading branches that can be up to 8″ (20 cm) in diameter.

The primary vegetative bodies (thalli) are crust-like (crustose) and ephemeral. They are usually absent in mature individuals. The secondary thalli are loosely attached, prostrate to ascending, cylindrical, 1⁄32″ to 1⁄16″ (1 to 2 mm) thick branches (pseudopodetia). The pseudopodetia can be 1⅜″to 4″ (3 to 10 cm) in height, but they are usually no more than 2″ (5 cm) in height. They consist of a solid core of parallel, thread-like cartilaginous cells (hyphae), surrounded by a loose layer (medulla), beneath a protective outer cortex. They are usually thickly covered with gray, short, matted hairs, especially on the lower surface. Abundant small, ash gray, granular or scaly structures (phyllocladia) are produced, each containing a green photobiont. The phyllocladia are mostly rounded and flattened, and they are often overlapping.

Spore-producing reproductive structures (apothecia) occur frequently, mostly on the lateral branches. The apothecia are dark brown to blackish brown, convex, disc-shaped, and up to 1⁄32″ wide or wider.

Similar Species

 

Ecology

Substrate

Ground

Growth Form

Fruticose

Habitat

Open areas

Hosts

 

Distribution

Map
2/26/2026

Sources

24, 30, 83.

Biodiversity occurrence data published by: Minnesota Biodiversity Atlas (accessed through the Minnesota Biodiversity Atlas Portal, bellatlas.umn.edu. Accessed 2/26/2026).

The Consortium of North American Lichen Herbaria (CNALH) https://lichenportal.org/cnalh/index.php. Accessed 2/26/2026.

Mycology Collections Portal (MyCoPortal) https://www.mycoportal.org/portal/collections/index.php). Accessed 2/26/2026.

Stereocaulon tomentosum Fr. in GBIF Secretariat (2023). GBIF Backbone Taxonomy. Checklist dataset https://doi.org/10.15468/39omei accessed via GBIF.org. Accessed 2/26/2026.

Fink, B. (1910). The Lichens of Minnesota. United States: U.S. Government Printing Office.

Riddle, L. W. (1910). The North American Species of Stereocaulon. Botanical Gazette, 50(4), 285-304.

Occurrence

Common and widespread

Taxonomy

Kingdom

Fungi (Fungi)

Subkingdom

Dikarya

Phylum

Ascomycota (Sac Fungi)

Subphylum

Pezizomycotina

Class

Lecanoromycetes (Common Lichens)

Subclass

Lecanoromycetidae (Shield Lichens, Sunburst Lichens, Rosette Lichens, and Allies)

Order

Lecanorales (Shield Lichens, Rim Lichens, and Allies)

Family

Stereocaulaceae

Genus

Stereocaulon (Foam Lichens)

Mycobiont

Stereocaulon tomentosum

Photobiont

green algae other than Trentepohlia (primary); cyanobacteria, filamentous (e.g. Nostoc, Scytonema) (secundary, e.g. in cephalodia)

Subordinate Taxa

Numerous subspecies, varieties, and forms have been described. Authoritative sources vary widely in the number they recognize, from zero to more than thirty.

Synonyms

Stereocaulon alpestre

Stereocaulon botryocarpum

Stereocaulon paschale ssp. tomentosum

Stereocaulon paschale var. tomentosum

Stereocaulon tomentosum var. alpestre

Stereocaulon tomentosum var. compactum

Stereocaulon tomentosum var. tomentosum

Common Names

Eyed Foam Lichen

Woolly Foam

Woolly Foam Lichen

Visitor Photos

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Dan W. Andree

Woolly Foam 01

Bright & Light Colored Lichen...

I noticed it due to the odd coloration. Had it not been a light bright color I wouldn’t have paid much attention. It seemed to be doing well and was a good sized growth of it, but a lot of grasses in the way making difficult for photography etc. It was unusually light and bright with tiny brownish spots on it. Not a great image but the color of it made my white balance on my camera having difficulty capturing the true color, but somewhat close. Really nice colors and almost seemed to light up. There was the only one like this I seen. Almost seemed too illuminate, but just must have been color.

Woolly Foam 02

This is one other Woolly Foam image...

It’s an unusual color particularly for a plant this time of year. It was on a North facing slope the day had on and off overcast and the ground was moist from rain a few days earlier. … Compared to everything else in that immediate area it seemed almost out of place.

Woolly Foam 03

Here is another image of the Woolly Foam Lichen taken at a later date (11-13-25) than the previous ones.

So many interesting lichens etc.

Minnesota Seasons Photos

Slideshows

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Other Videos

Red mountain pass lichen, Ouray area. Stereocaulon tomentosum.
Mike's thoughts on plants.

About

Aug 16, 2021

This is an unexpected lichen more common in cool wet areas, which might describe the pass frankly but I have seen it in peat bogs. Never makes the wine glasses of Cladonia or the white hedges of Cladinia.

Visitor Sightings

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Dan W. Andree
11/13/2025

Woolly Foam

Location: Norman Co. Mn.

Here is another image of the Woolly Foam Lichen taken at a later date (11-13-25) than the previous ones.

So many interesting lichens etc.

Dan W. Andree
10/26/2025

Woolly Foam

Location: Norman Co. Mn.

I noticed it due to the odd coloration. Had it not been a light bright color I wouldn’t have paid much attention. It seemed to be doing well and was a good sized growth of it, but a lot of grasses in the way making difficult for photography etc. It was unusually light and bright with tiny brownish spots on it. Not a great image but the color of it made my white balance on my camera having difficulty capturing the true color, but somewhat close. Really nice colors and almost seemed to light up. There was the only one like this I seen. Almost seemed too illuminate, but just must have been color.

Minnesota Seasons Sightings