Ragbag Lichen

Ragbag Lichen (Platismatia glauca) is a large foliose lichen of the family Parmeliaceae that hangs and sprawls from branches in loose, thin, ragged sheets, often 5-20 cm across and sometimes forming dense drapes on well-lit conifer limbs. The common name captures the impression it makes: an untidy bundle of torn grey rags.

The thallus is only loosely attached, so lobes lift, twist and overlap freely rather than pressing flat to the bark, and the thin leathery tissue rustles when dry. Margins are strongly wavy, crisped and often torn, and they crumble into a fringe of granular propagules.

Platismatia is distinguished from the more familiar appressed grey lichens by this loose, ruffled, almost fruticose bearing combined with a mottled pale-and-dark lower surface, and P. glauca is by far the most widespread species of the genus in the northern hemisphere.

Thallus and lobes

The thallus is foliose but very loosely attached, forming thin, flexible, overlapping sheets 5-20 cm across with lobes 5-20 mm wide. Lobes are irregularly divided and their edges are strongly crisped, wavy and frequently torn, giving a ragged silhouette.

Upper surface

Pale grey to bluish-grey or greenish-grey, smooth to shallowly wrinkled, occasionally browning where exposed. Along the margins and lobe edges the surface breaks up into abundant coarse isidia and granular soredia, forming a crumbly, granular fringe that is the most useful hand-lens character.

Lower surface

The underside is mottled — patchy pale cream to white and dark brown to black — usually paler toward the lobe tips and darker centrally, with sparse or absent rhizines, matching the loose attachment.

Texture and fruiting

The tissue is thin, leathery and pliable when wet, papery and brittle when dry. Apothecia are rare, brown and marginal; reproduction is almost entirely by the marginal isidia and soredia.

Ragbag Lichen grows on the branches, twigs and trunks of conifers — spruce, fir, pine, hemlock, larch and Douglas fir — and on birch, alder, oak and other acid-barked broadleaves, and occasionally on mossy rock and old timber. It prefers humid, well-lit conditions and reaches its greatest luxuriance on the outer branches of trees in oceanic and montane forests, upland birchwoods, conifer plantations and cloud-catching ridges.

The distribution is broadly circumboreal and temperate: western and northeastern North America, much of northern and western Europe including Britain and Scandinavia, and northern and montane Asia. It is perennial and evergreen, present in every season, and appears fullest and softest during prolonged wet weather.

As an epiphyte, Platismatia glauca takes no nutrition from the trees it grows on. The fungal partner forms the thin ragged thallus and the green algal partner photosynthesises within it, while water, minerals and nitrogen are absorbed straight from rain, fog and canopy drip across a very large surface area relative to the lichen's mass.

Its loose attachment and brittle dry tissue mean fragments break away readily, and this — together with copious marginal isidia and soredia — drives rapid local colonisation of new twigs. The accumulated sheets contribute litter and nutrients to the forest floor and provide shelter and nesting material for canopy invertebrates and birds. Its sensitivity to prolonged drying keeps it concentrated in humid, oceanic and upland settings.

Platismatia norvegica shares the loose ragged habit but has a strongly ridged and pitted upper surface with isidia concentrated along the ridges rather than an evenly granular crisped margin. Cetrelia species are similar in size and grey colour but are smoother, flatter and more regularly rounded in lobe outline, with conspicuous white pseudocyphellae dotting the upper surface.

Parmelia sulcata is grey but closely appressed, with a white reticulate ridge network and a black, densely rhizinate underside, quite unlike the mottled, near-rhizine-free lower surface of Ragbag. Hypogymnia physodes, often growing beside it, has hollow inflated lobes and a uniformly black rhizine-free underside, and lacks the crisped granular margins.