Iceland “moss,” Cetraria islandica

Cetraria islandica, a true lichen known as Icelandic moss, captured as an ingredient in “Icelandic schnapps.”

An unexpected encounter last week reminds me to talk about one of my favorite lichens! Cetraria islandica is not entirely rare in Colorado, but I would guess it’s rarely seen by most of us. For one thing, it occurs at higher elevations, above, say, 8000 ft. (~2440 m) It’s also cryptically colored, blending in with the forest floor, where it can be confused with other small plants, mosses, and lichens carpeting the soil.

Steeped in alcohol, "Iceland moss" becomes Icelandic schnapps—definitely an acquired taste.

Steeped in alcohol, “Iceland moss” becomes Icelandic schnapps—definitely an acquired taste.

But the lichen I encountered last week, at a friend’s house, was in a bottle, lending flavor and perhaps substance to a concoction called Icelandic schnapps. Of course, I had to taste it, and he was kind enough to oblige. Knowing he had laboriously carried it home from a visit to Iceland, I did not ask for a second glass.

Cetraria islandica is one of a few species of this genus known to occur in Colorado, although they will be more common at higher altitudes (or latitudes!). All are fruticose, after a fashion, and more or less brownish in color. (Clarity is helped here by the fact that the yellowish species are now in a separate genus: Flavocetraria.)

According to CNALH: “Cetraria ericetorum is distinguished from C. islandica … by having a consistently P- medulla, and by the pseudocyphellae being strictly marginal and sometimes indistinct or absent. Cetraria ericetorum ssp. reticulata belongs within the C. ericetorum complex comprising three mainly geographical races. Subspecies. reticulata basically comprises the subspecies occurring in North America.”

A third species, Cetraria aculeata is more truly tangled and shrubby, its branches more rounded than flattened. It was once in a separate genus, called Cornicularia.

ID Tips for Lichen Newcomers

How do you start figuring out lichens if you’re a novice, especially if you have no keys? With 85% of my books, including lichen ID materials, still in storage (long story), I’m thrown on the resources of the internet. Here are a few suggestions for exploring lichen basics (off-site links open in a new window):

Guide to British Lichens on Twigs, with picture key! Click to go to site.

Guide to British Lichens on Twigs, with picture key! Click to go to site.

There is an online lichen key from the UK for 60 British lichens on twigs (from the Natural History Museum at South Kensington); they also have a glossary of terms. To get started, choose whether the lichen is fruticose, foliose, or crustose. (See descriptions at our Shapes and Sizes page if you’re not sure.) You eventually get to a color photo of the lichen. If you get one or more results, don’t assume the species is right, but it might at least point you to a genus to check out. (I got a lot of “no results” on my searches, but I was just making up characters.)

You might try checking photos at Ways of Enlichenment, which does a good job of showing many species in each genus.

Steve Sharnoff offers some lichen basics at his website. He also has lots of photos available that may also be helpful, but this site is focused on North America. Some species, however, are widespread, and many genera are.

If you narrow it down to a few species, you can check whether they occur in your area at this database maintained by the Consortium of North American Lichen Herbaria (CNALH). Their records include specimens from all over the world. If you go to their dynamic map and click on your area (and specify a radius to search), they will generate a checklist that you can also use as an interactive key. Very nice!!

Only the lichen portal at CNALH will give you a detailed description of important characters, but at least the others provide visual references.

Note: Also posted this on iNaturalist as a journal entry.

The Latest Lichen News

Yes, we’re back, and there’s news in the world of lichens. Please forgive the long “dormancy,” of which more is explained below. But right now, things are popping in the world of lichens, and we thought we’d better attempt to update ourselves just a tad.

The Overlooked Organisms That Keep Challenging Our Assumptions About Life, at The Atlantic. As they say, “Gorgeous and weird, lichens have pushed the boundaries of our understanding of nature—and our way of studying it.” (by Ed Yong Jan 17, 2019)

[Or maybe not so “latest” after all. Here’s an earlier article about the researcher who put this idea together, Toby Spribille, also by Ed Yong, in the Atlantic in 2016.]

We’ve talked before about the fact that some lichens contain multitudes—specifically, representatives of not just two but THREE kingdoms within their symbiosis. Now, researchers are demonstrating that the situation for some lichens may be even more complex.

Hooray for lichens—the organisms that continually surprise us!

Lichen-forming fungi [all*] belong to a group called the ascomycetes. But in 2016, Spribille and his colleague Veera Tuovinen, of Uppsala University, found that the largest and most species-rich group of lichens harbored a second fungus, from a very different group called Cyphobasidium. (For simplicity, I’ll call the two fungi ascos and cyphos).

Bright green Letharia vulpina outshines pale Usnea in this photo from C. Tom Hash (, used by permission).

Bright green wolf lichen (Letharia vulpina) outshines pale Usnea (beard lichens) in this photo from C. Tom Hash (, used by permission).

Look on the bark of conifers in the Pacific Northwest, and you will quickly spot wolf lichens—tennis-ball green and highly branched, like some discarded alien nervous system. When Tuovinen looked at these under a microscope, she found a group of fungal cells that were neither ascos nor cyphos. The lichens’ DNA told a similar story: There were fungal genes that didn’t belong to either of the two expected groups. Wolf lichens, it turns out, contain yet another fungus, known as Tremella. —Ed Yong

* There are, as I understand it, a few lichen-forming Basidiomycetes as well. But for practical purposes… ascomycetes.



Tremella is commonly known to us ordinary mortals as “witches’ butter” and is a parasitic jelly fungus that seems to be fairly distinctive. I posted this photo on iNaturalist, however, and haven’t had anyone confirm its identity to date.

Tremella fungi had been reported from wolf lichens previously, but were thought to be “secondary” to the main symbiotic relationship. The “news” here is that these extra fungi may, in fact, be quite central to the concept we call lichens. At least in the genus Letharia. We’ll be staying tuned to new developments!

Yes, I’ve recently been getting active on iNaturalist (@slwhiteco), and am especially intrigued by checking out the lichens there. Unfortunately for me, lichen taxonomy has changed significantly since I studied them back in the Darkish Ages. Apparently the advent of DNA analysis has stimulated, or required, major revisions in groups, and I’m still trying to untangle the implications. Perhaps we’ll explore a few of them in a future post.

My other complicating factor is that I’m no longer in Colorado. The move, and preparations for it, were a significant distraction from this website, but we’ll hope to bring you more lichen material in the future. Sadly, other than several Cladonia and some corticolous species, I’ve not found good lichen-hunting in this part of upstate New York yet.