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.

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.