Key to Common British Native Ferns

By Adrian Dyer and Alison Evans


This identification key covers the most common and widespread fern species native to Britain and Ireland. There are in addition some very rare species that are unlikely to be found by any but the most committed fern hunters. These are listed in the Appendix
Further details for identifying all these species are given in Merryweather (2020), Hutchinson and Thomas (1996); Page (1997); and Merryweather (2005, 2007). Assistance with the more difficult identifications may be obtained from The Plant Crib (Rich, T.C.G and Jermy, A.C., 1998, published by BSBI) which is available on-line.
Although now recognised as the closest relatives of ferns, all horsetails have been omitted from this key. Most published identification aids include the 8 horsetail species and their several hybrids, but their structure, and their diagnostic characters, are very different from ferns and beginners are advised to take one step at a time and become familiar with one group before tackling the other.

Access the Key here

It is important to choose mature, fertile fronds. If taking a frond for identification, take the full length of the stipe. Avoid fronds that are sterile (i.e. are not producing spores), damaged or are smaller than the majority of fronds present. With practice, ferns can often be identified from sterile fronds, but beginners will find this more difficult


Hutchinson, G. and Thomas, B. A. (1996) Welsh ferns. National Museums and galleries of Wales, Cardiff.
Jermy, C. and Camus, J. (1991) The Illustrated Field Guide to Ferns and Allied Plants of the British Isles. Natural History Museum, London.
Merryweather, J. (2005) Key to Common ferns. Field Studies Council,Shrewsbury.
Merryweather, J. (2007a) The Fern Guide. Field Studies Council, Shrewsbury.
Merryweather, J. (2020) Britain’s Ferns, Clubmosses, Quillworts, and Horsetails. A field guide. Princeton WILDguides. ISBN 9780691180397
Page, C. N. (1997) The Ferns of Britain and Ireland. Second Edition. CUP, Cambridge.

APPENDIX: The less common species omitted from the Key

The 9 rare native British and Irish species are restricted to very few sites and in some cases to very few individuals

Anogramma leptophylla (L.) LinkJersey FernAdiantaceae
Asplenium onopteris L.Western SpleenwortAspleniaceae
Cystopteris diaphana (Bory) BlasdellWintergreen Bladder FernWoodsiaceae
C. montana (Lam.) Desv.Mountain Bladder Fern
Ophioglossum azoricum C. Presl.Small Adder's TongueOphioglossaceae
O. lusitanicum L.Least Adder's Tongue
Trichomanes speciosum Willd.Killarney FernHymenophyllaceae
Woodsia alpina (Bolton) S.F.GrayAlpine WoodsiaWoodsiaceae
W. ilvensis (L.) R.Br.Oblong Woodsia

The 6 scarce native species are absent from most of Britain and Ireland, and confined to a limited habitat range, but may be locally common within their restricted distribution

Adiantum capillus-veneris L.Maidenhair FernAdiantaceae
Asplenium obovatum Viv. subspecies lanceolatum (Huds.) P.Silva (= A. billotii)Lanceolate SpleenwortAspleniaceae
Athyrium distentifolium TauschAlpine Lady FernWoodsiaceae
Dryopteris cristata (L.) A.GrayFen Buckler FernDryopteridaceae
D. submontana (Fras.-Jenkins & Jermy) Fras.-JenkinsRigid Buckler Fern
Pteridium pinetorum C.N.Page & R.R.Mill.Northern BrackenDennstaedtiaceae
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