A deciduous fern of cracks, fissures and scree in limestone rock, but also found in shallow grikes of limestone pavement, and, rarely, on chalk. It prefers warm, sunny exposures but can tolerate light shading. It has become established as a garden escape on walls and culverts. Lowland to 585 m at Carreg yr Ogof (Carms.).
The distribution of this species is stable. Some sites have, however, been lost through competition with Mercurialis perennis and Crataegus monogyna, while quarrying and overgrazing have had detrimental effects on others.
Circumpolar Boreo-temperate element, with a disjunct distribution.
Count of 10km squares in Great Britain: 113
Count of 10km squares in Ireland: 1
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: -0.37
Scarce Atlas Account
Gymnocarpium robertianum (Hoffm.) Newman
This fern is confined to calcium-rich substrates and usually grows on natural limestone screes and pavement. It is usually found on Carboniferous and oolitic limestone, but there is at least one locality on hard chalk. It is favoured by open sunny situations, although it may get established in shady grikes. G. robertianum is associated with other limestone species such as Asplenium viride, Cystopteris fragilis, Geranium robertianum, Mercurialis perennis, Oxalis acetosella and Phyllitis scolopendrium. It rarely grows above 450 metres altitude, but reaches 585 metres on Carreg yr Ogof in the Black Mountains.
This perennial species is easily grown from spores and is a favourite with fern gardeners. It often escapes and establishes itself on man-made walls and in culverts even in the drier and colder parts of the country.
In its natural habitats G. robertianum can be ousted by competition with Mercurialis perennis and hawthorn scrub, and limestone quarrying has taken its toll of its localities.
This is a circumboreal species. In Europe it is most frequent in central Europe, extending south to the Pyrenees and north to northern Norway (Jalas & Suominen 1972).
A. C. Jermy
PLANTATT - Attributes of British and Irish plants. (.zip 1455KB) This dataset was compiled and published in 2004, and last updated in November 2008. Download includes an Excel spreadsheet of the attributes, and a PDF explaining the background and nomenclature. Note that the PDF version is the booklet as published, whereas the Excel spreadsheet incorporates subsequent corrections. A hardcopy can be purchased from the Centre for Ecology and Hydrology.
Atlas text references
1988. The Irish Red Data Book. 1. Vascular Plants.
1986. Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
Jalas & Suominen (1972)
1978. Ferns and their allies. The Island of Mull: a survey of its flora and environment. :12.1-12.7.
1965. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 1. 2 vols.
1997. The ferns of Britain and Ireland, edn 2.
1994. Scarce plants in Britain.