The descriptive text, below the map, is from the Cornish Red Data Book (2009). The map on this web page depicts the organisms distribution and shows the records made pre-2000 and those made since.
Found on dry, vertical or overhanging, east or north-facing rock faces near the sea. Rarely on serpentine on the Lizard, but much more commonly on the acidic, granite rocks of West Penwith and the Isles of Scilly. Very local in the extreme south-west of Britain. Cornwall and the Isles of Scilly represent the stronghold for this species in Britain.
I.J. Bennallick, S. Board, C.N. French, P.A. Gainey, C. Neil, R. Parslow, A. Spalding and P.E. Tompsett. eds. 2009. Red Data Book for Cornwall and the Isles of Scilly. 2nd Edition.Croceago Press.
The Cornish Red Data Book Project was led by the Cornwall and Isles of Scilly Federation for Biological Recorders (CISFBR). The full text and species accounts (minus the maps) are available on the CISFBR website.