Powdered Ruffle Lichen

Powdered Ruffle Lichen (Parmotrema hypotropum) is a large foliose lichen of the family Parmeliaceae, forming loosely attached rosettes 5-20 cm across whose broad lobes lift and ruffle away from the bark at the edges. Parmotrema as a genus is characterised by exactly this look — big, wide, loosely appressed lobes with wavy, often ciliate margins — and it is well represented in warm-temperate and subtropical regions.

P. hypotropum is one of the most frequently encountered members of the genus in the southeastern United States, where it decorates the twigs and trunks of hardwoods in open woodland and suburban settings.

Its identification rests on a tidy combination of three margin features: a fringe of black cilia projecting from the lobe edges, a dense white rim of granular soredia along and just inside those edges, and a lower surface that is black in the centre but leaves a broad naked brown zone around the margin.

Thallus and lobes

The thallus is foliose and loosely attached, spreading 5-20 cm across, with broad rounded lobes 5-15 mm wide whose margins are wavy, crisped and lifted well clear of the substrate — the ruffled effect of the common name.

Margins

The lobe edges carry scattered to abundant black cilia — short stiff eyelash-like hairs — and are densely edged with granular white to grey-white soredia that form a continuous powdery rim, often curling the margin slightly upward and inward.

Upper surface

Pale grey to whitish grey, sometimes faintly greenish when wet, smooth to gently wrinkled, without white ridging or conspicuous pale dots across the face.

Lower surface

Black over the central portion with sparse black rhizines, but with a wide, smooth, naked brown to pale brown marginal zone free of rhizines. Lifting a lobe to see this bare brown border is one of the best confirmations.

Fruiting bodies

Apothecia are infrequent in sorediate populations; when present they are brown cupped discs with a thalline rim. Soredia dominate reproduction.

Powdered Ruffle Lichen grows on the bark and twigs of deciduous trees — oak, hickory, maple, sweetgum, elm, pecan and many others — and also on conifers, fence rails and occasionally rock. It favours open, well-lit, warm and humid situations: woodland edges, open oak-hickory forest, roadside and yard trees, orchards and coastal scrub.

It is most abundant in the southeastern and eastern United States, extending north and west in reduced abundance and occurring in comparable warm-temperate habitats elsewhere. Perennial and evergreen, it is present in all seasons; the ruffled lobes soften and green slightly when wet and stiffen to pale grey when dry.

This is an epiphytic lichen taking nothing from its host tree — the fungal partner constructs the thallus and holds it loosely to the bark with sparse central rhizines, while the green algal partner supplies carbohydrates. Water, minerals and nitrogen are absorbed directly from rain, dew and bark runoff over the broad lobe surfaces.

Because the lobes stand clear of the bark and are fringed with soredia, fragments and soredial granules detach easily in wind and rain, so colonies spread quickly along a branch and pieces knocked down in storms are commonly found on the ground below. Fallen thalli contribute organic matter and are collected by birds for nest construction, aiding dispersal further afield.

Parmotrema perlatum (P. chinense) is a very similar large grey ruffle lichen with marginal soredia and cilia, but its lower surface is black almost to the margin with only a narrow bare brown rim, whereas P. hypotropum shows a broad naked brown marginal zone. Parmotrema perforatum has perforated apothecia and lacks abundant marginal soredia.

Parmotrema crinitum and P. reticulatum carry cilia too, but P. crinitum bears isidia on the surface rather than a soredia rim and P. reticulatum has a network of fine cracks and white lines on the upper surface. Smaller Parmelia sulcata is separated by its white reticulate ridging, solid closely appressed lobes, dense black rhizines and complete absence of marginal cilia.