Ferns

Royal Ferns - Osmundaceae

European Royal Fern Osmunda regalis

Native in wetlands on St Mary's, Tresco and Annet.


Habit	Habit	Pinnules	Fertile leaf

Tree-ferns - Dicksoniaceae

Australian Tree-fern Dicksonia antarctica

Introduced from eastern Australia. Widely planted around Tresco Abbey Gardens with a few plants elsewhere on inhabited islands. Recorded as self sown on Tresco.


Habit	Habit	Pinnae	Pinna

Pinnules	Sori	Leaf detail	Trunk

Ribbon Ferns - Pteridiaceae

Common Maidenhair Fern Adiantum capillus-veneris

Formerly native in a few sea caves but now known only as an introduced population, growing on urban walls around Hughtown, St Mary's. The leaves bear fan-shaped pinnae, carried on fine, hair-like, blackish stems and are very distinctive. This plant is probably much better known as a houseplant in the UK but the wind-lashed plants around Hughtown are rather stunted compared with the graceful potplants of sheltered conservatories and windowsills.


Habit	Habit	Pinnae	Pinnae

Pinnae	Pinnae and young sori

Brackens & Allies - Dennstaedtiaceae

Common Bracken Pteridium aquilinum

Native. An abundant plant of both shady and sunny places on coastal heaths and uncultivated ground. Bracken spreads readily by underground rhizomes which push up fresh, bright green leaves in great quantity in the spring and which then die down in the autumn, the dead leaves turning cinnamon-brown and remaining through the winter. Easily told from all other ferns by its spreading habit, coupled with the two- to three-metre long leaves, which start as a single stalk, but then branch into three main sections. Ripe spores appear in autumn and are covered by inrolled leaf margins.


Habit	Pinna	Pinnules	Marginal sori

Spring shoots	Spring shoot	Spring shoot	Dead winter leaves

Buckler Ferns - Dryopteridaceae

Falcate Holly-fern Cyrtomium falcatum

(House Holly-fern) Introduced from warm-temperate eastern Asia as an ornamental and recorded from a number of locations around St Mary's, most often along shady hedgebanks and copses. The fronds are glossy with the pinnae untoothed or only toothed in the lower two-thirds of the leaf margin. Mature fronds have 3-11 pairs of pinnae. Sori are scattered across the underside of the leaves.


Habit	Young plant	Fronds	Pinnae

Sori

Soft Shield Fern Polystichum setiferum

Native. Found most frequently in mossy, damp ditches bordering woodland or along shady lanes and back roads. Widespread but generally uncommon. Spore-bearing fronds may be found from July to December. Overall, the leaf is rather soft to the touch and has a narrow outline with pinnae becoming only a little shorter towards the base before ending abruptly. Pinnules are sharply pointed with long teeth. The basal margins of the lowest pair of pinnules form an acute angle.


Habit	Leaves	Leaf base	Pinnules

Spores	Spores

Common Male Fern Dryopteris filix-mas

Native. A frequent clump-forming fern of shady places, found on all the inhabited islands and a few of the smaller islands. A deciduous species, with all of the leaves dying down over winter - thus, spring plants consist only of new, fresh green leaves. Leaves are narrower and more parallel-sided than those of Broad Buckler Fern and the pinnules have less sharply-pointed tips. Compared with Scaly Male Fern, the pinnules are more sharply pointed and they tend to taper slightly towards the tip.


Habit	Pinnules	Spore cases

Scaly Male Fern Dryopteris affinis aggregate

Native. The male ferns have been reviewed in recent years, such that the true status of the various forms has yet to be fully established. Scaly Male Fern consists of a difficult group of plants that are very closely related but their full taxonomy is still open to debate. It is most likely that they represent apomictic species that produce clonal populations, but for now, they are represented by Scaly Male Fern, which here represents the general group where the plant cannot be assigned to one of the subspecies. There also follows, details of two subspecies that have been record on Scilly and which form relatively distinct populations; these are Golden-scaled Male Fern and Borrer's Male Fern. Unlike Common Male Fern, these are more or less evergreen species - thus, spring plants consist of both new, fresh green leaves and old, dark green leaves. Leaves are narrower and more parallel-sided than those of Broad Buckler Fern and the pinnules have less sharply-pointed tips. Compared with Common Male Fern, the pinnules are very rounded at the tip and have more or less parallel sides. At the base of the pinnules, there is a dark, blackish mark. The scales at the base of the leaf stalk are plentiful and very obvious.

Note: All of the Dryopteris affinis photos here were taken on the mainland but are used here to aid identification of any plants that might be found on the Isles of Scilly.


Habit	Habit	Leaf stalk scales

Pinnules	Dark pinnule mark	Spore cases

Borrer's Male Fern Dryopteris affinis ssp. borreri

Native. Identification details under Scaly Male Fern also apply to this subspecies. Leaves narrow a little towards the base but end abruptly, with the lowest pinnae about half as long as those half way along the leaf. The scales on the leaf stalk are less plentiful than those of Golden-scaled Male Fern and are typically a pale straw colour. The basal pinnule on each pinna is typically a little longer than the one next to it, well toothed on the margins and with a distinct lobe at the base. Pinnules are often conspicuously toothed at the 'shoulder'.


Basal leaf section	Pinnules	Pinnules	Leaf stalk scales

Golden-scaled Male Fern Dryopteris affinis ssp. affinis

Native. Identification details under Scaly Male Fern also apply to this subspecies. Leaves narrow towards the base, with the lowest pinnae less than half as long as those half way along the leaf. The scales on the leaf stalk are plentiful and are a golden-brown colour. The basal pinnule on each pinna is about the same size as the one next to it, only vaguely toothed on the margins and without a distinct lobe at the base. Pinnules are typically round-tipped and not toothed at the 'shoulder'.


Habit	Pinnules	Pinnules

Leaf stalk scales	Leaf stalk scales

Broad Buckler Fern Dryopteris dilatata

Native. In shady places on all of the larger islands. Spore-bearing fronds may be found from late May to August. Overall, the leaf has a broad outline with the longest pinnae half way down the leaf and becoming shorter towards the base. Pinnules end in sharply pointed teeth with incurved tips. The scales at the base of the leaf are pale with an obvious, dark centre.


Habit	Habit	Leaf	Pinnae

Pinnules	Pinnules	Basal scales	Spores

Narrow Buckler Fern Dryopteris carthusiana

Native. Formally on St Mary's, Tresco and Bryher, but not recorded since 1993. Spore-bearing fronds may be found from late May to August. Overall, the leaf has a relatively narrow outline with the lowest pairs of pinnae being the longest and the leaf having a noticeably long stalk. Pinnules end in sharply pointed teeth with incurved tips. The scales at the base of the leaf are pale, without dark centres.


Habit	Leaf	Pinna	Pinnules

Pinnules	Pinnules	Basal scales	Spores

Lady Ferns - Athyriaceae

Common Lady Fern Athyrium filix-femina

Native. Frequent on St Mary's and Tresco in damp, shady places. Ripe spores present in late autumn. A graceful species with delicately and finely cut leaves. Leaves in outline are broadest about the middle, with a pointed, long-tapered tip. Pinnules have deeply lobed and toothed margins. The spores are covered by an indusium which is either linear, or more often curved or J-shaped in outline.


Habit	Leaf	Young leaf	Pinnae

Pinnae	Pinnules	Spores covered by indusium	Ripe spores

Polypodies Ferns - Polypodiaceae

Kangaroo Fern Lecanopteris pustulata

(Phymatosorus diversifolius, Zealandia pustulata) Introduced from Eastern Australia and New Zealand. Long-established in damp woodland on Tresco and St Mary's. Forms extensive creeping mats. Younger plants have simple leaves, gradually acquiring more lobed leaves with age.


Habit	Leaves	Leaves	Leaves

Leaf underside	Leaf underside	Sori

Intermediate Polypody Polypodium interjectum

Native. Widespread and the commonest of the two polypody species on the islands. Frequently found on old walls, where it is more tolerant of limey mortar than is Common Polypody. Ripe spores present in late autumn or early winter. The leaf shape tends to be broadest about the middle and tapers toward each end and the pinnae are somewhat pointed at the tip. Under high magnification, the spore cases can be seen to consist of two halves, held together by a ribbed 'strap'. In Intermediate Polypody, this strap has on average 7-9 (extreme 4-13) ribs or bands, while Common Polypody has on average 10-14 (extreme 7-17) ribs.


Habit	Habit	Leaf	Leaf underside

Sori on underside of leaf	Magnified view of sori and ribbed straps

Common Polypody Polypodium vulgare

Native. Widespread on the larger islands but less common than Intermediate Polypody. Ripe spores present in late autumn or early winter. The leaf shape tends to be more or less evenly wide throughout much of its length, tapering more sharply toward each end and the pinnae are rather blunt at the tip. Under high magnification, the spore cases can be seen to consist of two halves, held together by a ribbed 'strap'. In Intermediate Polypody, this strap has on average 7-9 (extreme 4-13) ribs or bands, while Common Polypody has on average 10-14 (extreme 7-17) ribs.


Habit	Leaves	Sori on underside of leaf	Magnified view of sori and ribbed straps

Manton's Polypody Polypodium x mantoniae

Native. Probably under-recorded but could occur in shady places or on walls. The leaf is rather variable in appearance and may often be rather uneven or distorted in overall shape, but they often resemble those of Intermediate Polypody in being widest about half way along the length of the leaf. Under high magnification, the spore cases can be seen to consist of two halves, held together by a ribbed 'strap'; this strap has on average 9-10 ribs or bands. Manton's Polypody is a hybrid between Common and Intermediate Polypody and is sterile, so no yellow or orange spores will be found and the sori will be seen to be empty when viewed under high magnification.


Habit	Leaf	Sori on underside of leaf	Magnified view of sori and ribbed straps

Hard Ferns - Blechnaceae

European Chain Fern Woodwardia radicans

Native to the western Mediterranean region and Macaronesia. Natutalised in shady woodland on Tresco. The name 'chain fern' comes from the unusual venation of the leaves which creates oval shapes that look like the links of a chain.


Habit	Habit	Leaf	Leaf

Pinnules	Leaf venation

Common Hard Fern Struthiopteris spicant

(Blechnum spicant) Native. A rare species, recorded sporadically from Tresco and St Mary's. Spore-bearing fronds may be found late summer onward. A small species, with leaves growing to 20-60cm in length. Leaves are of two types, all being just once-pinnate, without pinnules. The outer leaves are sterile and arch outward, while the inner leaves are narrower, fertile (bearing the spores) and stand upright in the centre of the plant.

Note: Most references will place this species in the genus Blechnum. The taxonomy here follows the specialist work of the Pteridophyte Phylogeny Group.


Habit	Habit	Leaf	Pinnae

Fertile leaves

Greater Hard Fern Parablechnum cordatum

(Blechnum cordatum) Introduced from South America. Long-established in damp woodland on Tresco and St Mary's. Forms extensive creeping mats. Lousley wonderfully describes the St Mary's population as being "In a malodorous ditch under elms"! Plants have separate fertile and sterile leaves with the spores carried in continuous strips on the underside of the fertile pinnae.

Taxonomic Note: For a long time, this species was misidentified as Chilean Hard Fern Parablechnum chilense (Blechnum chilense) and it is still wrongly sold under that name in the horticultural trade. This has resulted in many botanical books and floras giving false information about the natural distribution and/or identification of these plants (including Stace and Sell & Murrell). Greater Hard Fern is native to northern and central South America while Chilean Hard Fern is native to the southern cone of Chile and Argentina and the neighbouring Juan Fernandez and Falkland Islands.


Habit	Habit	Sterile leaf	Sterile pinnae underside

Sterile pinna detail	Fertile leaf	Fertile leaf	Sori

Spleenworts - Aspleniaceae

Sea Spleenwort Asplenium marinum

Native. Found throughout the islands, mostly on outer facing, oceanic coastlines but also on walls and buildings.


Habit	Habit	Habit	Habit

Leaf	Pinnae	Developing sori	Mature sori with spores

Maidenhair Spleenwort Asplenium trichomanes

Native. Local and has declined in recent years, but small populations persist on walls on St Mary's, St Agnes and St Martin's. The long, narrow leaves with rounded pinnae and black midribs are distinctive.


Habit	Leaves	Pinnae	Ripe sori with spores

Lanceolate Spleenwort Asplenium obovatum subsp. lanceolatum

Native. Most frequent on walls on St Mary's and St Agnes with scattered records from other islands, though strangely missing from St Martin's.


Habit	Habit	Leaf	Leaf

Pinnules	Pinnules and sori	Pinnules and sori

Common Black Spleenwort Asplenium adiantum-nigrum

Native. Widespread on all inhabited islands and several of the smaller islands. Plants in sunnier places often turn golden-bronze in colour.


Habit	Habit	Leaf	Leaf

Wall-rue Asplenium ruta-muraria

Native. Rare on walls, with just two, small populations known on St Mary's and St Martin's. A very distinctive fern that has a blue-green colour to its leaves, which resemble the leaves of garden rue (Ruta graveolens).


Habit	Habit	Leaf	Ripe sori with spores

Common Hart's-tongue Asplenium scolopendrium

Native. Scattered on the larger islands and most common on St Mary's. A very distinctive fern, being our only native species with highly glossy leaves that are entire and not at all divided. The spore-bearing sori on the underside of the leaves appear as a series of narrow, dark, parallel lines. This plant is evergreen and the old leaves can get browned and very tattered over winter before the new leaves emerge in spring. Plants may form large clumps with leaves up to 60cm long in shady woodland, but are much smaller when growing on walls.


Winter	Summer	Fresh leaves	Spores in slit-like lines

Rustyback Fern Asplenium ceterach

Native. Very rare in the islands and only recorded from St Martin's, where last reported in 1992. The leaves have distinctive pinnae that are broadest at the base and merge into the midrib without stalks. The underside of the leaves are covered in papery scales and turn rust-coloured as the spores ripen.