Bottlebrush Frost Lichen

Physconia detersa is one of two similar lichens that share the common name Bottlebrush Frost Lichen. The other is Physconia leucoleiptes. Both species are common in Minnesota, are similar in appearance, and grow on both bark and rock. They are best distinguished by the shape of the marginal soralia and by chemical spot tests. Some sources do not separate the two species.

Bottlebrush Frost Lichen (Physconia detersa) is a very common, very widespread, medium-sized lichen. It occurs throughout the Northern Hemisphere including Europe, Asia, Greenland, and North America. It occurs throughout the United States except in the deep south. It is very common in Minnesota. It grows on tree bark, on rock, and on moss over rock.

The vegetative body (thallus) is leaf-like (foliose), divided into radiating lobes (a rosette), and usually up to 2¾″ (7 cm) in diameter, rarely up to 3½″ (9 cm) in diameter. It is held to the substrate by black, branched, root-like structures (rhizines). The lobes are long with straight sides (linear), usually rounded at the tip, sometimes irregular. They can be 1 ⁄32″ to ⅛″ (1 to 3 mm) wide, but they are usually no more than 1 ⁄16″ wide. The upper surface is shiny and gray to brownish-gray when dry, greenish brown when moist.

Cortex-free areas of the thallus (soralia), mostly on the margins, produce reproductive growths (soredia). Soralia sometimes develop on other parts of the thallus, appearing as fissures on the surface. The soralia usually merge together, becoming continuous. The soredia may be finely granular, or it may be in clusters with an outer protective layer. Usually the lobe ends, and occasionally almost the entire thallus, are covered with pale, powdery, flour-like soredia, giving them a frost-like appearance. This is the feature that gives the genus its common name “frost lichens.”

The underside of the thallus is dark brown to black near the center and dark tannish brown toward the lobe ends, almost never white.

Bottlebrush Frost Lichen infrequently produces disk-like spore producing structures (apothecia). When present, they are 1 ⁄32″ to ⅛″ (1 to 3 mm) in diameter.

Trees, rock

Foliose

Sources

4, 7, 24, 26, 29, 30, 77, 81.

The map at left shows the counties with records or observations of Physconia detersa in dark green. These counties may also have records or observations of Physconia leucoleiptes. The counties in light green have records or observations of Physconia leucoleiptes but not of Physconia detersa.

Widespread and very common

The taxonomy of Bottlebrush Frost Lichen is far from resolved.

Index Fungorum, LichenPortal, NCBI, NatureServe, and iNaturalist list both Physconia detersa and Physconia leucoleiptes as valid full species. NatureServe and iNaturalist separate them by hyphenating the word Bottle-brush for the latter species.

MycoBank lists Physconia detersa as valid and Physconia leucoleiptes as a synonym of Parmelia pulverulenta var. leucoleiptes.

ITIS lists Physconia detersa but not Physconia leucoleiptes or Parmelia pulverulenta var. leucoleiptes.

Catalog of Life does not list any of these names.

Location: Cass County

lichen on rock

Location: Cass County

Location: Cass County