A large, foliose lichen of shady sites in old woodlands, dull grey or yellow-green when dry but bright grass-green when wet.
Large, to 10cm diameter, with a thallus of closely adpressed, thin, rosette forming lobes. The upper surface is a dull grey-green ro grey-brown colour when dry, with a smooth, almost oily appearance, but bright green when wet. The lower surface is almost white with a fine, brown tomentum. Thallus lobes are short, narrow and unridged (like a "Parmelia"), 3-10mm wide. The inner lobes are incised and contorted, the marginal lobes rounded at the apices and smooth. There are no soralia or isidia, but occasionally few to numerous marginal folioles.
Apothecia are usually abundant, and when young appear as volcano-like swellings which open out to expose the brown disc with a warted margin. The spores are colourless, becoming brown when mature, persistently 1-septate, 25-45 x 8-11 ?m.
Spot reactions negative but sometimes K+ faint yellow and KC+ faint pink. Contains scrobiculin.
Habitats On broad-leaved trees, especially oak, ash, sycamore, hazel, elm and beech. Mostly confined to ancient woodlands and parklands, occasionally on sheltered rocks in woods and on western sea-cliffs. This is the most oceanic and shade tolerant of the British Lobaria species.
An important member of the Lobarion, particularly in more shaded, sheltered sites where it occurs with Lobaria pulmonaria, Sticta spp and Nephroma spp.
Bron: British Lichen Society