Hammered Shield Lichen

not listed

NNR - Unranked

not listed

Hammered Shield Lichen is a widespread, abundant, weedy lichen. It occurs across the northern hemisphere, in southern Africa, and in Australia. It is very common in Minnesota. It grows on the bark of deciduous and coniferous trees in relatively open habitats, disturbed sites, and agricultural lands. It also grows on mossy rock, but only rarely grows on soil.

The vegetative body (thallus) is leaf-like (foliose), greenish-gray to whitish-gray, more or less circular in outline, and divided into branches (lobes). The lobes are flat, 1 ⁄16″ to 3 ⁄16″ (2 to 5 mm) wide, widely spreading, overlapping, and touching but separate, not fused together. The tips are abruptly squared, as if cut off (truncate). The upper surface is shiny but sometimes has a white, flour-like or frost-like covering (pruinose). It has abundant powdery granules (soredia). It does not have shiny granules (isidia). It may be smooth but usually has a network of sharp ridges and depressions giving it a “hammered” appearance. This is the feature that gives the lichen its common name. It has minute, elongated, rounded openings (pseudocyphellae), and sometimes develops cracks along prominent pseudocyphellae. The lower thallus surface is black and is moderately to densely covered with black, unbranched root-like structures (rhizines). When wet, the thallus can usually be removed intact with a knife.

Hammered Shield Lichen rarely produces disk-like spore producing structures (apothecia). When present, they are 1 ⁄16″ to 5 ⁄16″ (2 to 8 mm) wide and have a dark brown disc.

Trees

Foliose

Open habitats, disturbed sites, and agricultural lands.

Trees and mossy rock.

Crottles are various lichens that were used to make dyes. Parmelia sulcata, sometimes called “Powdered Crottle”, was used as the source for a reddish-brown dye.

Sources

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

Widespread and abundant

Location: Superior Hiking Trail, Cook County