A blue-grey to silvery foliose lichen, becoming bronze-tinged as it ages. The lobes have conspicuous white pseudocyphellae which form a fine network. Thallus 4 to 20cm in diameter.
Found on the branches and trunks of trees, only occasionally on rocks. Widespread and common.
Photograph of Hammered Shield Lichen (Parmelia sulcata), taken February 2012 on dead deciduous wood, local wood, Staffordshire. © Pete Hillman 2012. Camera used Panasonic Lumix DMC-FZ38.