Ferns and fern-allies (=Pteridophytes)

Ferns are flowerless plants that reproduce by spores, but unlike Mosses and Liverworts they have vascular (water conducting) tissue that allows them to colonise drier sites and to grow taller to >1 m. They are diverse in structure.

Note that ferns are classified into several families: Marseliaceae, Ophioglossaceae, Azollaceae, Woodsiaceae, Thelypteridaceae, Cystopteridaceae, Athyridaceae, Aspleniaceae, Pteridaceae, Hymenophyllaceae, Osmundaceae, Blechnaceae, Dryopteridaceae, Onocleaceae, Polypodiaceae, etc.

Other Pteridophytes are Horsetails , Clubmosses and Quillworts


Two keys to ferns are provided:
A. Based on plant form and B. based on Fruiting structures

Plant form: Select one of these eight groups

Simple fronds
+/- Fan-shaped or forked
Lobed or 1-Pinnate leaves
2- or more Pinnate leaves

Floating, tiny
Moss-like, hanging
Resembling clover
Azolla filiculoides
Marsilea quadrifolia

See also:


Fruiting structures: select from 4 options

Reproductive structures:

(a) distinct from vegetative:



(b) Linear sporangia (or solid spore masses)

Asplenium marinum
Asplenium trichomanes
Asplenium viride
Asplenium adiantum-nigrum

Asplenium ruta-muraria
Asplenium septentrionale
Asplenium ceterach

(c) Sporangia comma-shaped to circular

Phegopteris connectilis
Oreopteris limbosperma
Gymnocarpium robertianum
Gymnocarpium dryopteris

Anogramma leptophylla
Cystopteris fragilis
Woodsia ilvensis
Woodsia alpina

Polypodium interjectum
Polypodium vulgare
Athyrium filix-femina
Athyrium distentifolium

Dryopteris felix-mas
Dryopteris affinis
Dryopteris carthusiana
Dryopteris aemula

Dryopteris expansa
Dryopteris submontana
Dryopteris carthusiana
Dryopteris dilatata

Polystichum aculeatum
Polystichum setiferum
Pteridium aquilinum

(d) Sori under edge of pinnules

Thelypteris palustris
Pteridium aquilinum
Oreopteris limbosperma

Frond/leaf form (8 options):

Simple entire fronds

Asplenium scolopendrium
Ophioglossum vulgatum

Small ferns (<30 cm high) with fronds or leaflets +/- fan-shaped or forked

Adiantum capillis-veneris
Asplenium ruta-muraria
Cryptogramma crispa

Asplenium septentrionale

Deeply lobed or singly pinnate leaves (any pinnules +/- entire)

Asplenium ceterach

Polystichum lonchitis
Asplenium marinum
Asplenium trichomanes
Asplenium viride

Onoclea sensibilis
Blechnum cordatum

Delicate small pinnate ferns (<c.20 cm)


Slightly larger pinnate ferns (to c.40 cm), generally not growing in tufts

Gymnocarpium robertianum
Gymnocarpium dryopteris
Asplenium adiantum-nigrum

Cryptogramma crispa
Adiantum capillis-veneris

Mostly tufted larger pinnate ferns (to 120cm or more)

. . . Choose according to plant form, or leaf form

By plant form:

Ostrich fern
Lemon scented fern
Male ferns
Shield ferns

Key to leaves of tufted larger ferns (to 120cm)

Polystichum aculeatum
Polystichum setiferum
Athyrium filix-femina
Athyrium distentifolium
Hard Shield-fern
Soft Shield-fern
Alpine Lady-fern
Dryopteris aemula
Dryopteris affinis
Dryopteris filix-mas
Dryopteris oreades
Hay-scented Fern
Scaly Male-fern
Mountain Male-fern
Dryopteris carthusiana
Dryopteris dilatata
Dryopteris expansa
Dryopteris submontana
Narrow Buckler-fern
Broad Buckler-fern
Northern Buckler-fern
Rigid Buckler-fern
Matteucia struthiopteris
Pteridium aquilinum
Oreopteris limbosperma
Thelypteris palustris
Ostrich Fern
Lemon-scented Fern
Marsh Fern
Osmunda regalis
Royal Fern

Pteridaceae/Adiantum . . . . Maidenhair Fern

Adiantum capillus-veneris . . . . Maidenhair Fern

Lvs often apparently fan-shaped or pinnate but with dichotomous branching; local, in moist sheltered spots, esp. in limestone grykes in W Br and W Ire

The similar A. raddianum has horseshoe-shaped, rather than linear, sporangia.

Compare also the pale-stemmed Yellow Corydalis:

Pteridaceae/Anogramma . . . . Jersey Fern

Anogramma leptophylla . . . . Jersey Fern

Rare on shady banks in Jersey; young seedlings of Black spleenwort can be similar

Aspleniaceae/Asplenium . . . . Spleenworts

Asplenium adiantum-nigrum . . . . Black Spleenwort

Triangular leaves, long petiole, branches alternating & with characteristic long thin sori

To distinguish A. adiantum-nigrum (bottom) and A. obovatum (top):

Asplenium obovatum . . . . . Lanceolate Spleenwort

Similar to Black Spleenwort, but with petiole << frond, sori shorter; Common in CI & SW En (esp. coastal); more local elsewhere

Asplenium ceterach . . . . Rustyback Fern

Previously Ceterach officinarum; common on base-rich substrates and mortar in walls in Ire & S & W Br, less common in E & N

Asplenium marinum . . . . Sea Spleenwort

Rock crevices by the sea around the coast exc. SE Br

Asplenium ruta-muraria . . . . Wall-rue

Common on walls

Asplenium scolopendrium . . . . Hart's-tongue Fern

Common in woodland

Asplenium septentrionale . . . . Forked Spleenwort

A rather local evergreen fern of acidic rocks and metalliferous mine spoil, esp. in Wa, Lake District and a few places in N Br, also Galway

Asplenium trichomanes . . . . Maidenhair Spleenwort

Common on walls; black midrib (sometimes split into a number of subspp)

Asplenium viride . . . . Green Spleenwort

Rather local on damp upland rocks on base-rich soil; like A. trichomanes but with green midrib

Athyriaceae/Athyrium . . . . Lady-fern

Athyrium distentifolium . . . . Alpine Lady-fern

Sori usually without indusium; Local on acid scree and in gullies mostly above 600 m in C & N Sc

Athyrium filix-femina . . . . Lady-fern

Characteristic C- or J-shaped indusium over spores

Salviniaceae/Azolla . . . . Water Fern

Azolla filiculoides . . . . Water Fern

Naturalised and floating on water bodies around the BI

Blechnaceae/Blechnum . . . . Hard Fern

Blechnum cordatum . . . . Greater Hard Fern

An uncommon garden escape, esp in SW Br & Ire

Blechnum spicant . . . . Hard Fern

Common on heathland and mountains; has distinct fruiting frond (see centre of third pic)

Ophioglossaceae/Botrychium . . . . Moonwort

Botrychium lunaria . . . . Moonwort

Dry, mostly upland, grassland, in Br and Ire, esp. N & W Br

Botrychium nordicum . . . . Moonwort

Clearly toothed lvs; rare - a population has recently been identified at Glenshee Ski centre, but may be more widespread

Pteridaceae/Cryptogramma . . . . Parsley Fern

Cryptogramma crispa . . . . Parsley Fern

Rocky mountains on acid soils

Dryopteridaceae/Cyrtomium . . . . House Holly-fern

Cyrtomium falcatum . . . . House Holly-fern

grown in conservatories but nat. on shady walls and rocks in W Br

Cystopteridaceae/Cystopteris . . . . Bladder-ferns

Delicate ferns with generally 3-pinnate triangular leaves

Cystopteris fragilis . . . . Brittle Bladder-fern

Shady basic rocks and walls, esp. in N & W esp. at higher altitudes; veins end at tips of teeth

Very similar are:

Cystopteris diaphana . . . . Diaphanous Bladder-fern

Rare on shady rocks and walls, in Devon, Cornwall and SW Ire; veins end in notches between teeth (c.f. C. fragilis)


Cystopteris dickieana . . . . Dickie's Bladder-fern

Rare on shady rocks in NC Sc, esp. sea caves in Aberdeen; pinnae and pinules strongly overlapping

Cystopteris montana . . . . Mountain Bladder-fern

Leaves triangular, with lowest pinnule largest, borne singly on long rhizomes; very local on wet rock gullies above 700 m in C Sc

Other rare subspp. include C. dickieana (basic wet rocks in E Sc)

Dryopteridaceae/Dryopteris . . . . Male and Buckler-ferns

Dryopteris affinis agg. . . . . Scaly Male-fern

Pinnules parallel-sided (c.f. D. felix-mas); note black spot on underside at junction of pinnules, flattened tip of pinnules: often split into 3 subsp. (D. affinis subsp. affinis, D. affinis subsp. cambrensis and D. affinis subsp. borreri; the latter with very truncated tips to pinnules)

Dryopteris felix-mas . . . . Male-fern

Throughout BI in woods; pinnules tapering with rounded ends

Dryopteris aemula . . . . Hay-scented Fern

Local in shady woods and ravines in Ire and W Br; frond bright green with crinkly appearance, winter green; scales long, evenly red-brown, often torn; pinnules concave on upper side, lowest pinnule larger (arrows)

Dryopteris oreades . . . . Mountain Male-fern

Usually <50cm, stiff crinkly lvs; rocky places on mountains; only top 1/2 of frond fertile with sori usu. only on the basal 1/2 of pinnules, indusia edges 'tucked under'

Dryopteris (cont) . . . . Buckler-ferns

Dryopteris carthusiana . . . . Narrow Buckler-fern

Grows from runners (not tufts); Wet woods and marshes throughout BI; stalk as long as rest of frond (which is not triangular); blunt pale brown scales

Dryopteris dilatata . . . . Broad Buckler-fern

Tufted, common in woods and shady places across the BI; 3-pinnate, dark green lvs with dark pointed stem scales with pale edges; pinnules 'droopy' (see pic. 4)

Dryopteris expansa . . . . Northern Buckler-fern

Locally common in upland scree and woodland in Sc, N Wa and N En; paler yellow than D.dilatata; triangular fronds, flat pinnules with lowest pinnule on basal side >1/2 length of its pinna

Dryopteris submontana . . . . Rigid Buckler-fern

Lvs stiff, greyish mealy with white hairs; plants like small shuttlecocks; local almost entirely on limestone in NW En

Cystopteridaceae/Gymnocarpium . . . . Oak Fern

Gymnocarpium dryopteris . . . . Oak Fern

Quite common in damp woods or shady places in N & W Br

Gymnocarpium robertianum . . . . Limestone Fern

Local on screes or rocks on limestone in En and Wa; petiole greenish/brown rather than black; glandular-hairy stems/fronds

Hymenophyllaceae/Hymenophyllum . . . . Filmy-ferns

Filmy ferns (Hymenophyllum)- in very damp shaded areas, esp. in Ire and W, only:

Hymenophyllum tunbridgense . . . . Tunbridge Filmy-fern

Veins not to edge of frond; toothed indusium see fig.1

Hymenophyllum wilsonii . . . . Wilson's Filmy-fern

Less common than H. tunbridgense; veins extend to margin; untoothed indusium

Marsileaceae/Marsilea . . . . Clover Fern

Marsilea quadrifolia . . . . Clover Fern

Grown in ferneries but not known in the wild

Onocleaceae/Matteucia . . . . Ostrich Fern

Matteucia struthiopteris . . . . Ostrich Fern

Naturalised in shady places scattered around the BI

Onocleaceae/Onoclea . . . . Sensitive Fern

Onoclea sensibilis . . . . Sensitive Fern

Naturalised in a few shady places around the BI

Ophioglossaceae/Ophioglossum . . . . Adder's-tongue Fern

Ophioglossum vulgatum . . . . Adder's-tongue Fern

Grassland, dune-slacks etc, mostly in lowlands throughout Br. Two smaller species occur rarely near the sea - O. azoricum and O. lusitanicum

Thelypteridaceae/Oreopteris . . . . Lemon-scented Fern

Oreopteris limbosperma . . . . Lemon-scented Fern

Characteristic undersurface of lvs; note also strong tapering to base of frond

Osmundaceae/Osmunda . . . . Royal Fern

Osmunda regalis . . . .Royal Fern

A tall robust, broad-lvd ferm of marshy areas with fruiting fronds distinct mostly in W Ire and W Br but as far S as CI

Thelypteridaceae/Phegopteris . . . . Beech Fern

Phegopteris connectilis . . . . Beech Fern

Shady, acid soils, fairly common in N & W Br; note lowest pinnae reflexed

Marsileaceae/Pilularia . . . . Pillwort

Pilularia globulifera . . . . Pillwort

On mud/shallow water scattered across BI but esp. in W & S Br and W Ire; distinguished from rushes etc. as has no lf sheaths

Beware - young plants of Eleocharis acicularis look similar but have faint lf sheaths & a well-developed rhizome:

Polypodiaceae/Polypodium . . . . Polypody

Polypodium vulgare . . . . Polypody

Common thoughout Br & Ire; round 'sori' (Pic.3) (Pic.3)

Polypodium interjectum . . . . Intermediate Polypody

Common in the S (e.g. the sp. in Jersey); often on calcareous substrates (e.g. mortar); N.B.angled oval 'sori' (Pic.3) (cf. pic.3 of P. vulgare)

Also P. cambricum (S polypody), which has lf blades <2x as long as wide and hairs mixed with the sporangia; less common and hard to distinguish from the above

Dryopteridaceae/Polystichum . . . . Shield-ferns

Note sharp/hairy points to pinnules:

Polystichum aculeatum . . . . Hard Shield-fern

More upland and N than P. setiferum; base of pinnules makes acute angle (Fig 3); frond narrows to base with short stipe

Polystichum lonchitis . . . . Holly Fern

Local on mountains (mostly above 600 m) in basic crevices esp. in N En and Sc and W Ire

Polystichum setiferum . . . . Soft Shield-fern

Frequent in wet woods in CI, S and W Br and Ire; ; base of pinnules makes right-angle (Fig 1)

Dennstaedtiaceae/Pteridium . . . . Bracken

Pteridium aquilinum . . . . Bracken

Shoots single - but invasive over large areas. Sori inrolled along edges of pinnules.

Thelypteridaceae/Thelypteris . . . . Marsh Fern

Thelypteris palustris . . . . Marsh Fern

Frequent only in E Anglia, scattered in BI N to C Sc; sori at edge of pinnules

Woodiaceae/Woodsia . . . . Woodsia

Tiny 2-pinnate mountain ferns with pinnae divided nearly to midrib; W. ilvensis (more) hairy and with more elongated pinnae

Woodsia alpina . . . . Alpine Woodsia

Rare mountain fern, primarily on basic rocks in C Sc; pinnae not elongated

Woodsia ilvensis . . . . Oblong Woodsia

Very local mountain fern of crevices up to about 700m; the long thin scales on the pinnae midrib are diagnostic and the more elongated pinnae

Mosses and Liverworts