Killarney fern (Trichomanes speciosum)

Killarney fern frond
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Killarney fern fact file

Killarney fern description


This distinctive fern is one of three European species with translucent (semi-transparent) leaves. There can be as many as several hundred leaves, growing from the creeping root, depending on the size of the plant colony. The Killarney fern was only discovered in 1724.

Trichomanes remarquable.
Leaf length: 200-350 mm

Killarney fern biology

Uniquely, Killarney fern occurs in two forms in the UK. One is called a gametophyte, is more common, and is the sexual form of the plant. This is perennial, capable of spreading vegetatively, and found in dark caves or crevices. It was only discovered in the UK in 1989. The other form is called a sporophyte, is much rarer, and is the ferny form of the plant.


Killarney fern range

This fern is found mainly in Ireland, Brittany (north-western France), the Canaries, Madeira and the Azores. In Britain it is found in two stages, one of which is rare and found from a few sites in the west of the country. The other, more numerous stage, is widely scattered, but more common in the west.

You can view distribution information for this species at the National Biodiversity Network Atlas.

Killarney fern habitat

Killarney fern requires a humid, frost-free environment, and in Britain, is restricted to shady, sheltered ravines with waterfalls, or places with similar conditions.


Killarney fern status

Classified as Vulnerable in the UK. Protected under Schedule 8 of the Wildlife and Countryside Act (as amended). Listed unded Annexes II and IV of the Habitats Directive, and Appendix 1 of the Bern Convention.

IUCN Red List species status – Least Concern


Killarney fern threats

During the Victorian period in the UK, there was a craze for collecting ferns from the wild, in order to grow them for ornamental purposes. It is likely that the rare Killarney fern was over-collected, and has not been able to recover its populations back to former numbers.

Today, there may be further threats from eager collectors and photographers, and activities which alter the humidity and the water quality of the sites.


Killarney fern conservation

Discovery of the differing forms of the plant has lead to an increased interest in the Killarney fern. It is listed in the UK Biodiversity Action Plans (UKBAPs), and included in English Nature's Species Recovery Programme (SRP).

Surveys across the country have revealed new sites of the fern, and genetic research has enabled more effective conservation measures. Although the sporophytes are still rare, there are fewer fears now about the future survival of the Killarney fern. However, it could still fall prey to collectors, and the fern is strictly protected by law.

The UK Biodiversity Action Plan for this species is available at UK BAP.
There may be further information about this species available via the National Biodiversity Network Atlas.


This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:


Plants that live for at least three seasons; after an initial period they produce flowers once a year.
Vegetative reproduction
Type of asexual reproduction (reproduction without recombination of genetic material) that results in the propagation of plants using only the vegetative tissues such as leaves or stems. The resulting plant is genetically identical to the original plant. A well-known example of this is the reproduction of strawberry plants from 'runners'.


  1. IUCN Red List (June, 2013)

Image credit

Killarney fern frond  
Killarney fern frond

© David Tipling /

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