Trichomanes speciosum | Killarney Fern



Conservation status

Future Prospects
Overal Assessment of Conservation Status
Overal trend in Conservation Status

Source: NPWS 2013.

IUCN Conservation Status
Ireland (1)*
Europe (2)
Least Concern
Global (2)
Least Concern

Sources: (1) Curtis, T.G.F.. and McGough H.N. 1988; (2) Bilz, M. 2011.

* This Red List is acknowledged as needing to be updated. The Red List category shown is updated from that appearing in the original 1988 document, due to changes in the Red List categories.

Legal status

Protected by the following legal instruments:

  • Habitats Directive [92/42/EEC] Annex II, Annex IV
  • Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention) Appendix I
  • Wildlife Act (1976)
  • Flora Protection Order 1999
  • Wildlife (Amendment) Act (2000)
  • The Conservation (Natural Habitats, etc.) Regulations (Northern Ireland) 1995.

Native status


Species Biology


One of a small number of native ferns whose sporophyte has translucent leaf blades as, apart from veins, the blades are only one cell thick.

The Killarney Fern (Trichomanes speciosum) is the only native fern with translucent leaves whose sporophyte has fronds over 10cms, usually 10-20cms (including frond stalk).

The rhizome of Killarney Fern is thicker than other native fern species that have translucent leaf blades (Hymenophyllaceae family, both other species of the genus occuring in natively in Ireland have thin, hair-like rhizomes).

The mid-rib of the Killarney Fern is winged for much of its length, the mid-ribs of the other two native  Hymenophyllum species are not.

Sources: Page, C.N. 1997; Stace C., 1997.


The Killarney Fern is generally a plant of almost permanently moist / humid, sheltered situations. Low light intensity is a typical feature of where it is found. Usually a species of acidic rock faces, it does grow on trees once the light intensity, shelter and moisture conditions are met.

Source: Page, C.N. (1997)

Habitats include but are not necessarily limited to;

  • Exposed siliceous rock (ER1)
  • Non-marine caves (EU1)
  • Wet Pedunculate oak - ash woodland (WN4)
  • Oak-birch-holly woodland (WN1)
  • (Mixed) Broadleaved woodland (WD1)

Sources: Page, C.N. 1997; NPWS, 2013; Fossitt, J.A. 2001.


The Killarney Fern (Trichomanes speciosum) displays classic alternation of generations, with a diploid sporophyte generation and a haploid gametophyte generation. In the case of ferns such as the Killarney Fern the sporophyte is the obvious 'plant' identified in the field.

The sporophyte generation produces spores. A spore, on germination produces a 'prothallus' containing male and female organs, the haploid gametophyte generation. Following fertiliztion a prothallus develops from which a new sporophyte develops

In the Killarney Fern, spores are ripe usually in July September, however in the Britain and Ireland spores are rarely produced.

Unusually for a fern the gametophyte generation is filamentous, and can persist at sites in the absence of the sporophyte generation due to the ability to produce gemmae, an asexual method of propogation.

Source: Page, C.N. 1997

Threats faced

Outdoor sport and leisure activities, recreational activities
Taking / removal of terrestrial plants, general
Problematic native species*
Invasive non-native species**

* e.g Brambles (Rubus fruticosus agg.)

**e.g. Rhododendron (Rhododendron ponticum), Cherry Laurel (Prunus laurocerasus)

Source: NPWS 2013.

The Threats identified in the Article 17 reporting document accord well with those Threats identified at a European Level for the species in the IUCN Red List Version 2014.2 however, at a European level some other threats are indentified:

  • Abstraction of surface water
  • Droughts

 Source: Bilz, M. 2011

Conservation actions

 In the Article 17 Habitats Directive reporting for the period 2007-2012 no Conservation Measures in place or in the process of being implemented during the period were listed for this species other than;

  • Continued legal protection of the species and its habitats inside and outside of Natura 2000 sites.

During the reporting period an All Ireland Species Action Plan for the Killarney Fern was produced by the National Parks and Wildlife Service / Northern Ireland Environment Agency (NPWS / NIEA, 2008). This includes specific measures for conservation of the Killarney Fern.  Access details for the Species Action Plan are included in the 'References' section below.

Source: NPWS, 2013.

In the IUCN European regional Red List Assessment  the following Conservation Actions were suggested;

  • Constant monitoring of the populations
  • Guidelines for forest management and water abstraction nearby the populations.
Source:Bilz, M. 2011.


World distribution(GBIF)

Limited distribution worldwide, found mostly in Ireland, British Isles and the west of Europe. Other recorded populations include the islands of Madagascar and the Canaries, Indonesia and Malaysia.

Accuracy of world distribution shown in the Global Biodiversity Information Facility (GBIF) map below will be constrained by, amongst other factors, data held but not shared by countries and organizations not participating in the GBIF.

Irish distribution

Widespread but sparse distribution away from the flat central plains. Greater focus in the south / south west of the country with smaller pockets  of records in the west, north and east. Some records wil be for gametophyte only.

Distribution frequency in Ireland

Temporal change

Records submitted to Data Centre in 2024

The following map is interactive. If you would prefer to view it full screen then click here.

How can you help

The National Biodiversity Data Centre is trying to improve our knowledge on the distribution of the Killarney Fern (Trichomanes speciosum) in Ireland. Should you observe the species, please submit sighting to add to the database. Detailed observations will assist us gaining a better insight into where the species is most abundant in Ireland and we might also be able to detect regional variations. Please submit any sightings and photographs at:

All records submitted on line can be viewed on Google Maps – once checked and validated these will be added to the database and made available for conservation and research.

Further information

For further information contact Dr. Liam Lysaght



Bilz, M. 2011. Trichomanes speciosum. The IUCN Red List of Threatened Species. Version 2014.2. <>. Downloaded on 30 September 2014.

Curtis, T.G.F.. and McGough H.N. (1988) The Irish Red Date List 1 Vascular Plants. Wildlife Service, Dublin.Published by The Stationery Office.

Fossitt, J.A. (2001) A Guide to Habitats in Ireland. The Heritage Council.

NPWS (2013) The Status of EU Protected Habitats and Species in Ireland.  Species Assessments Volume 3. Version 1.0. Unpublished Report, National Parks & Wildlife Services. Department of Arts, Heritage and the Gaeltacht, Dublin, Ireland.

NPWS / NIEA  (2008) All Ireland Species Action Plan Killarney Fern

Page, C.N. (1997) The Ferns of Britain and Ireland, 2nd Edition.Cambridge University Press.

Stace, C. (1997) New Flora of the British Isles, Second Edition. Cambridge University Press.