About SLWhite

Dabbling in many, too many, things.

Old Man’s Beard, the Genus Usnea

Long pendulous thallus of Usnea cavernosa, found on conifers in Rocky Mountain National Park, the San Juan Mountains, and other high elevations in Colorado. Not common here; this scan is of a specimen from Idaho.

Some fruticose lichens form long webs, dangling from tree branches, that acquire common names like “tree hair” or “old man’s beard,” especially in places like the Pacific Northwest, where high humidity and tall trees support their robust expression. From a distance, these resemble the “Spanish moss” of southern states (which is neither moss nor lichen).

Common species of Usnea, such as U. hirta and U. subfloridana, occur on conifer bark and are small and shrubby.  At higher elevations with adequate moisture, larger species like U. cavernosa may be seen.

Common species of Usnea, such as U. hirta and U. subfloridana, occur on conifer bark and are small and shrubby. At higher elevations with adequate moisture, larger species like U. cavernosa (at top) may be seen.

More common in our Colorado forests are species of Usnea that display themselves less dramatically. Most are no more than a few inches tall (or long) and are frequently seen on bark of conifers like Douglas-fir and Colorado or Engelmann spruce. (Oddly, however, not on ponderosa pine.)

A closer view of this same specimen is below; click to enlarge further.

A close-up of the same lichen shows the tangled branches characteristic of the Usnea thallus. Each branch has a tough central cord, which distinguishes this genus from other light-green arboreal species.

A close-up of the same lichen shows the tangled branches characteristic of the Usnea thallus. Each branch has a tough central cord, which distinguishes this genus from other light-green arboreal genera, like Evernia and Ramalina.

Detailed description of Usnea cavernosa
More Usnea photos (at Ways of Enlichenment)
List of Usnea species and photos (at Sharnoff Lichens)

Peltigera leucophlebia

Or is it Peltigera aphthosa? Only by peeking underneath can you be sure! This post was published as a lichen profile in the Winter 2013 issue of Aquilegia, newsletter of the Colorado Native Plant Society (Vol 37, No. 6). Back issues are available online at the CoNPS website..

Peltigera leucophlebia, Peltigera aphthosa

Photo by Rick Brune.

Photo by Rick Brune.

Broad, ruffled lobes would place the abundant “pelt” lichens among the most noticeable of our montane lichens, were it not for their usual cryptic brown and gray coloring. Fortunately three of our 15 species stand out, at least when wet, thanks to the chlorophytes that are their primary photobionts. Peltigera aphthosa and Peltigera leucophlebia (clear veins) are large lichens with bright green coloring that helps us spot them when the forest floor is moist. The 2-4 cm wide lobes radiate to form a thallus 30 cm or more across.

To distinguish these two species, you’ll probably have to take a peek at the underside. P. leucophlebia, as its name implies, has distinct veins that change from light colored near the margin to black toward the center. Carefully loosen the lichen from the soil or mosses to check for this. In P. aphthosa, the veins tend to be broad and undefined. The uplifted lobes bearing brownish apothecia have, in P. aphthosa, green cortex on the underside of these reproductive structures, but in P. leucophlebia, the cortex is absent or present only as green specks on the white background.

Fun fact: Round dark structures on the upper surface, called cephalodia, contain cyanobacteria, giving these lichens claim to a three-kingdom symbiosis.

Don’t be fooled: Species of Sticta look like Peltigera and are in the same family, but the underside is black with white spots instead of the characteristic veins. Our third green Peltigera, P. venosa, is smaller (less than 2 cm diameter) and each fan-shaped thallus consists of a single lobe, usually with black marginal apothecia.

Scans of upper (left) and lower (right) surfaces of Peltigera leucophlebia, by Richard Brune.

Scans of upper (left) and lower (right) surfaces of Peltigera leucophlebia, by Richard Brune.

Exploring our lichen world

Several of us took a field trip yesterday to look at lichens and specifically to find lichens that were especially interesting and unusual. We succeeded completely! In our group was a new member of the Native Plant Society who had an interest in learning more about and photographing lichens, mosses, and other often overlooked small beings that we find in nature. His interest and talent have me spending time with the books again, refreshing all the things I used to know and picking up a few new ones in the process. He’s also promised to share his photos on this website soon.

Right before a sad mishap with my brand new camera, I caught this picture:

This lovely Peltigera aphthosa (or maybe P. leucophlebia) was not the most exciting lichen we saw all day, but it was the best, and pretty much the only, photo I captured. Being out looking at lichens means hope for an updated website here, but having a new photographer on board brings the certainty of MUCH better pictures! Stay tuned…