Colonsay Fern-appreciation Walks
Kevin Byrne offers a variety of guided walks and tours in Colonsay, details of which appear elsewhere. Kevin happens to have a particular interest in Ferns and this page is provided for the convenience of people who are kind enough to join his dedicated Fern-appreciation Walks. Although it includes some general information at the start, the real purpose of the page is to supplement the main walk with a simple "refresher" - most people come on the walk through Colonsay House Woodland Gardens and the route is recreated below so as to provide some additional information and perhaps jog the memory. Nearer the bottom of the page there is information about additional ferns in Colonsay, some of which might have been seen on one of the more ambitious walks. Please do not hesitate to tell Kevin about any errors on this site, he is on a learning-curve.
The walks through Colonsay House Woodland Garden are organised and led by Kevin Byrne with the kind permission of Colonsay Estate.
Ferns are non-flowering but, like flowers, have veins to transport xylem (water) and phloem (sugar and salts); they live by "alternation of generations", involving the sporophyte (spore producing) stage followed by that of the gametophyte (sexual plant), but the vital gametophyte generation is tiny and was long unknown. In ordinary speech, "fern" refers to the sporophyte generation since one would not normally even notice the other one. Most fern reproduction is vegetative, but spore dispersal aids colonisation.
Ferns may be epiphytic (growing on trees) without being parasitical for nutrition and some are epipetric (growing on rocks); they are largely resistant to attack by insects or grazing animals due to chemical repellants. They have limited economic value other than in horticulture and scientific research; bracken (Pteridium aquilinus) is now regarded as a scourge, but at one time was highly prized.
Ferns have their origin in the Carboniferous period (post Devonian, pre-Permian, c. 359 - 299 mya) when swampy conditions prevented decay of dead material and locked carbon into what became coal, peat and oil; flowering plants arose about 50m yrs later in drier conditions, more suited to seeds. The origins of most modern fern date back to the Cretaceous period (c. 145 - 65 mya) although both Horsetails and Royal Fern have older origins. There are about 36 species recorded for Colonsay but three or four of them have only been noted once or twice.
Ferns are among the Pteridophyta and we mostly notice the sporophyte generation since the gametophyte is so tiny. In the scientific norm, they are identified by a binomial system referring to their genus and species e.g. Polypodium vulgare . Fronds may be simple or compound (pinnate, bipinnate etc.) and they open by carcinate (or, less commonly, erect ) vernation . The rachis or spine of a simple frond is known as the costa . The ripe spores are often released from the sporangium by dehiscence - the annulus has certain thin walled cells which are primed to rupture with a change in humidity, creating a catapult. Photosynthesis is via the epidermis, with the rhizome as a food store for winter dieback. Nutrients are delivered via the vascular bundle in the stipe (the spine below the frond).
The lefthand illustration should be followed clockwise as a summary of the "alternation of generations"; the righthand illustration highlights some of the common terms used in describing ferns and is based upon an image of Polypodium vulgare in Billeder af nordens flora (1917) by Mentz and Ostenfeld
The life cycle of a fern:
From the above diagram, one can easily follow the interesting two-part life cycle of a fern. This starts with the sporophyte, the form with which we are familiar, whose fronds are so attractive. On the back of the fertile fronds there are tiny single-cell spores, in sporecases (sporangia), often protected by a cover (indusium). When ripe, the spores are catapulted free and if successful will germinate to form a tiny new body, called a gametophyte or prothallus. That completes stage 1, and the gametophyte may now produce on its underside two tiny structures, the archegonium (egg container) and the antheridium (producing sperm). When a drop of water is present the sperm can swim to the archegonium, to fertilise the egg and thus produce an infant sporophyte (zygote), to be fed at first by the decaying prothallus. When mature, the new sporophyte completes stage 2 of the cycle by producing new spores...
Key to Common Ferns by J Merryweather and C Roberts (Field Studies Council)
The Fern Guide by J Merryweather (F.S.C.)
The Ferns of Britain and Ireland by C N Page (Cambridge University Press)
British Ferns, Clubmosses, Quillworts and Horsetails by J Merryweather; this is a brilliant DVD, free on application to firstname.lastname@example.org
British Pteridological Society www.ebps.org.uk ; membership is not expensive and is very rewarding
Colonsay Fern-appreciation Walk ... an aide memoire
The basic walk starts at Kiloran, beside the Old Village Hall, and one goes along the track towards Pondside Cottage, turning left up a slight brae after 50 metres. At this corner, in season, there is a Lady Fern; sadly this one seems to be a little too exposed and is a late developer, but better examples will be found to be abundant as the species is prolific in Colonsay.
Lady-fern. Athyrium filix-femina (L.) Roth. The genus Athyrium includes about 180 species and the name means "without a shield" which is thought to refer to the insubstantial indusium (the membrane that protects the sorus); the species name means "female fern". It is not winter hardy, so for much of the year the site of this particular specimen is bare; although Athyrium filix-femina is the only member of that genus to be found in Colonsay it is one of the most common ferns that we have.
It is particularly common in woodland but will also be found in more open settings, and depending upon the location it is very variable in appearance. It is quite obviously a fern, the fronds are lanceolate, they may be up to a metre in height, and they grow from a shuttlecock. The stipe is about one third the length of the frond and not especially scaly. The frond is bipinnate and the pinnae are also lanceolate. The pinnules are lobed, toothed and have simple veining - the central main vein has alternating subsidiaries leading into the lobes and teeth. In an exposed location, such as this one, the fronds will look rather desiccated and less vibrant by comparison with specimens elsewhere.
In many cases, the Lady Fern can be identified at a glance because of its more delicate and graceful jizz, and the identification can be confirmed by reference to the very distinctive sori. These are arranged in two rows flanking the midrib and are variously described as "j" shaped, or as resembling commas. The indusium is attached only along one edge, and the free edge is toothed. (This species is best seen from early June.)
Beware of confusion with Male Fern Dryopteris filix-mas , Scaly Male Fern D. affinis agg. or Broad Buckler Fern D. dilitata .
At the top of the brae (20 metres) turn right and examine the stone gate pier for Wall Rue and Common Polypody.
Wall-rue. Asplenium ruta-muraria L. The genus Asplenium includes some 700 species, and the name originates with a Greek physician, Dioskorides (50 - 100 AD) who advocated the use of "spleenwort" in medicine; the species name means "wall rue". Colonsay has five species of Asplenium: Wall-rue, Black Spleenwort, Sea Spleenwort, Maidenhair Spleenwort and Hart's-tongue Fern.
Wall-rue is compact, bipinnate and bears an obvious resemblance to the flowering plant, Common Rue ( Ruta graveolens ), and at first glance it does not look "fernlike". It will be found in tufts on old walls with lime-rich mortar, especially gate piers and has thin, wiry roots that give the plant an excellent purchase. It is evergreen, but looks a little sad and dry in winter; frond length may be up to 10cm or so. New fronds appear in spring, being fresh and bright, slightly succulent. The stipe is about two-thirds the length of the frond and the rachis has alternate egg- or diamond-shaped pinnules on which the veining is fan-shaped rather than based upon a midrib. The creeping rhizome is short and dark, the stipe is shiny brown at the bottom and becomes green further up. The sori are linear and have indusia; when ripe the whole underside of the pinnule becomes covered in the proliferation of brown spores.
Although Wall-rue is very variable according to habitat, it is quite distinctive. Older fronds are more divided and very exposed locations may stunt the growth, as with some examples at Oransay Priory. (In Colonsay, it becomes very weather-beaten, shrivelled and desiccated by springtime and starts to flourish again from late May).
Common Polypody. Polypodium vulgare L. The genus Polypodium includes more than 75 species, and the name means "many feet", supposedly in reference to scars left along the creeping rhizome where fronds have decayed (said to suggest a centipede); the species name means "ordinary". Colonsay has two species, the other being Intermediate Polypody or Polypodium interjectum .
Polypody will be found on walls and rocks and, being epiphytic, will also be found growing independently on trees. The rhizome can be up to 60 cm long but is fairly thin, and is anchored by very strong roots. The fronds grow in a double row along the rhizome and may be up to 75cm in total length if in a good situation. The stipe accounts for between a quarter and one half of the length of the ovate-oval frond, which is deeply pinnatifid, each segment being well-defined and with a broad base. The holly-green frond is tough, almost leathery and evergreen.
Polypody is unmistakeable as a genus, and the species can usually be established by reference to the sori, which are naked (without indusia) and a cheerful orange when ripe. In a nutshell, the sori of Common Polypody are essentially round , whereas Intermediate Polypody has oval sori. Sometimes it is difficult to be certain, in which case microscopic examination of the spores will be required. Incidentally, a third species is Polypodium cambricum , which has linear sori; its most northerly outpost is in the isle of Lismore by Oban, and P. interjectum is the hybrid form between P. vulgare and P. cambricum . (Polypodium vulgare is best from mid-June).
The example on this pillar is a bit disappointing, but many better examples will be seen shortly.
Continue along the grassy track, noticing a fern beside the strainer post on the left; it is a better example of Woodland Lady-fern, Athyrium filix-femina. As you approach Pondside Cottage, there is from late June a nice example of Common Polypody on top of the wall to your left - as mentioned, this fern is an epiphyte, meaning that it can grow on rocks and trees, but it only uses them for support and is not a parasite.
Pass through the gate and notice on the left-hand side, at the foot of a low wall, a small Hart's-tongue Fern.
Hart's -tongue Fern. Asplenium scolopendrium L. Formerly included in the genus Phyllitis and associated with Polypodiaceae , it is now assigned to the spleenworts; by a twist of fate, the species name "scolopendrium" retains the link with the Polypodies, meaning "millipede". In this case the name is thought to refer to the very distinctive linear sori on the undersides of the frond, resembling the insect.
This is a common, unmistakeable fern growing in woods, on walls, in damp and shady places; it is especially fond of lime. It has a broad, undivided strap-like leathery frond up to 70cm long, usually of a bright, glossy green colour. The rachis forms a well-defined midrib, from which a multitude of fine veins emerge at right angles; the sori form double stripes or lines, somewhat resembling insects. The fronds rise as a shuttlecock from a short stocky rhizome. The sori are protected by indusia attached along just one side; when ripe the sporangia are reddish-brown.
This fern is flanked by examples of Lady Fern, Male Fern and Broad Buckler, all of which are discussed below. Walk on for a few paces, passing a set of steps on your left, and you will see numerous other examples of Hart's-tongue Fern, some of which are well developed; a few plants in this area have a frond which is divided at its apex (bifurcated), in contrast to the normal form. It is possible that this is a natural variety, but it is also possible that it is an example of a cultivar, since Hart's-tongue Fern has long been a particular subject of the horticulturalist's attentions.
Return to mount the steps and go about 10 metres towards the trees on your left, where by late-summer you will see a particularly healthy epiphytic Polypody growing on the base of a tree (just possibly P. interjectum ). Beyond it and a little to the left there is a splendid Scaly Male Fern, one of a group of closely related ferns raised to species level in recent years.
Scaly Male-fern. Dryopteris affinis agg . The genus Dryopteris includes about 250 species, the name means "oak fern" but is more usefully taken as simply "woodland fern". Within the Dryopteris genus there is a former complex or sub-group of morphotypes (distinguishable strains) of which the three most relevant to Colonsay are Dryopteris affinis affinis , D. affinis borreri and D. affinis cambrensis . (The common names created for them are Golden-scaled Male-fern, Borrer's Male-fern and Narrow Male-fern.) They are apomictic (reproduce asexually), and each spore has the same number of chromosomes as its parent; on germination a new sporophyte is produced directly from the gametophyte generation rather than by sexual fertilization of an egg cell. The morphotypes are very difficult to differentiate and non-specialists are advised to record the complex in general terms, as Dryopteris affinis agg.
As a matter of interest, some of the distinguishing features are tabled here:
Dryopteris affinis affinis
Dryopteris affinis borreri
Dryopteris affinis cambrensis
|Evergreen?||Nearly||Slightly||Not winter hardy|
|Fronds||v. firm, v. glossy||Not firm or glossy||Firm, slightly glossy|
|Scales||Dark gold, dense||
Pale gold, dark bases
Gold, reddish gold
|Stipe||15% - 20% frond||20% - 25% frond||15% - 20% frond|
Flat in plane
Flat in plane
Angled to plane
|Basal lobe of pinnae||Often insignificant||
Sometimes conspicuous and rectangular
Conspicuous and rounded
Thick, well tucked-under.
Thin, lifts, shrivels, goes to "chanterelle", falls away
Thin edges, tall, piecrust, splits radially, some may persist
As a complex, the Scaly Male Ferns are quite common in Colonsay. They are very similar to the Male Fern (Dryopteris filix-mas) but rather more robust, more leathery in texture and the stem is clothed in quite dense golden or brown scales . Fortunately, they do all have one good distinguishing feature in common: there is a noticeable black "spot" at the junction of each pinna midrib with the rachis. This is usually more obvious upon the under-surface of the frond of the living plant, but tends to fade quite quickly in any voucher specimen.
Kevin wonders if this particular example is Dryopteris affinis borreri, Borrer's Male-fern because it is reasonably winter hardy and has moderately dense golden scales when examined in early January; but it is probably safer to simply record it as D. affinis agg. until firmer identification is possible. Notice the scales in particular, for comparison with another specimen which lies a little further along the trail.
For contrast, see an example of Male Fern - plentiful in this area, although it seems to appear a little later than either the "Scaly Males" or the Lady Fern.
Male-fern. Dryopters filix-mas . The binomial name means simply "woodland male fern" and its gender reflects the fact that it was at one time believed to be the partner of the "lady fern". Both ferns are very common, grow from a shuttlecock, are of a similar size and die down in winter, but the Male Fern is more "masculine" at a glance and they actually belong to different genera.
The Male Fern is very like the Scaly Male Fern, but does NOT have the dark mark on the underside of the pinnae midribs at the junction with the rachis. The rhizome is short and erect, fairly prominent in winter. The stipe is between a quarter and a third the length of the frond, with fairly dense straw-coloured pointed scales . The individual pinnae are flat and even-sided, but slightly toothed at the edges which may be a little downturned; the tips are rounded with tiny acute teeth pointing to the apex. The sori are kidney-shaped with a thin, flat pale indusium which later turns to brown, forms a chanterelle shape and eventually falls away at spore maturity.
Supposedly Male Fern provided a cure for tapeworm, and it seems that Louis XVI was deceived into paying 16,000 francs to one Mme. Nouffer for the remedy, although it had been handed down from the time of Dioskorides, the 1st c. Greek botanist; it was still regarded as efficacious by 19th c. medical opinion in Scotland. Tragus (a.k.a. Hieronymous Bock, 16th c.) maintained that a piece of the rhizome would cure a sick horse if placed under the tongue; intriguingly, he also stated that it was used for other purposes "too scandalous to relate". It was used in dressing leather, and its ashes were used in bleaching linen. "Diverse vagabonds" used to prepare Lucky Hands or St. John's Hands from the rhizome and frond, which they sold to the credulous as protection against witchcraft.
Before turning back towards the steps, notice close at hand another distinctive shuttlecock fern, one which is very common in Colonsay, a Broad Buckler-fern.
Broad Buckler-fern. Dryopteris dilatata . This is another member of the Dryopteris genus and the suffix "dilatata" means "spread-out", in reference to the frond, which is like a shield or "buckler". Colonsay has eight species of Dryopteris in all, of which six are fairly common: Broad Buckler Fern, Male Fern, Hay-scented Buckler Fern and (collectively) the three species of Scaly Male Fern. The less common ones are Narrow Buckler Fern (Dryopteris carthusiana) and Dwarf Male Fern (Dryopteris oreades).
Broad Buckler Fern is quite common in woodland, especially in damp places - it is very obviously a fern, with vigorous fronds growing up to a metre in length in shuttlecock form from a stout, upright rhizome covered in the blackened remains of former frond bases. The frond is broadly triangular, becoming more lanceolate in more mature plants, about 30 cm at its widest, and normally bipinnate, sometimes tripinnate. The lowest pair of pinnae may be longer than the adjoining pair. The sori are paired on either side of the pinnae midribs and protected by kidney-shaped indusia. The stipe is about one third of the total length of the frond and is adorned by numerous brown scales the lower of which will be seen to have a central darker stripe backed by lighter edges . This feature is of great assistance as a defining mark, as is the fact that (unless in deep shade) the pinnules turn downwards at the margins, giving them a convex appearance.
Return to the steps and cross the avenue, passing a nice Hart's-tongue fern on the left, beside a piece of monumental granite. The granite was part of the undercroft of the monument to Lord Colonsay which was severely damaged by lightning, in September 1876. At the foot of the slope cross the Mill Burn, which powered a mediaeval mill belonging to Kiloran Abbey; the mill remained in use until 1865. There is a remarkable stand of Gunnera beside the bridge and you will also see Skunk Cabbage (Lysichiton americanus) growing along the opposite bank; this is also known as Swamp Lantern and it has been found useful in many ways, not least by bears who eat it as a laxative after a period of hibernation.
Having crossed the bridge, follow the path ahead but after a few metres turn right beyond the bamboo and cross a small ditch to admire a magnificent Scaly Male Fern.
This specimen is covered in a wonderfully thick coat of golden scales, and was in excellent condition in mid-January 2016 and, although it had something of a set-back die to neighbouring drainage work, it seems likely to recover. Note the very firm, very glossy fronds, the "flat in the plane" pinnae with "margins unlobed". Kevin is inclined to believe that this is an example of Dryopteris affinnis affinnis or Golden-scaled Male-fern.
The path continues onwards, passing large numbers of ferns on the right, all of which are winter-dormant, including numerous Broad Buckler Fern and Lady Fern with a sprinkling of Scaly Males. After 150 metres, one comes to a muddy drain and just beyond it a mature Tree Fern.
Soft Tree-fern. Dicksonia Antarctica . This is actually a native of eastern Australia, where it can grow to 15m in height in damp, sheltered woodland and similar habitats. The "trunk" is in fact the erect rhizome, forming the stipe; the canopy is said to consist of alternate rows of fertile and sterile fronds and apparently does so in this instance. It is frost-hardy to about -5 degrees C. , but very slow growing, just a few centimetres per annum, and therefore takes more than 20 years to reach maturity. It is named for an important Scottish nurseryman and botanist, James Dickson (1738 - 1822). Reputedly Tasmanian aborigines used it as a source of starch, although unfortunately the entire native population of Tasmania was annihilated by the colonialists following an initial massacre in 1828, so the information comes from indirect sources. It is said that the young crosiers can be consumed as food.
If one turns right at the Tree Fern, leaving the path but following the line of the drain, in about 20 yards one has been hoping to find Field Horsetail and just possibly Wood Horsetail. The very fine "Scaly Male" hereabouts is almost certainly Dryopteris affinis cambrensis , and there are examples of Blechnum spicant and B. Cordatum which will be mentioned in due course.
Wood Horsetail. Equisetum sylvaticum . The horsetails are true ferns, being vascular plants, unlike the "Fern Allies" with which they are often grouped, such as the Club Mosses ( Lycopodium and Selaginella ) which are bryophites and lack circulation systems for water and nutrients (xylem and phloem). The horsetails are rich in silica and have been valued for their abrasive qualities, ranging from pot-scouring to the most delicate work in fine-polishing by jewellers and watchmakers. In the days of gas lamps, Dutch Rush E. hyemale was used to provide inexpensive gas mantles, because the silica content enabled it to continue to glow incandescently even after it had been burnt. Curiously enough, horsetails absorb and retail heavy metals from the soil, including gold; apparently this was a feature valued by early prospectors in America, who would analyze the horsetails growing in potential areas before deciding where to stake their claim.
Wood Horsetail, an extraordinarily attractive plant, is unfortunately not as common as one might wish, and it is distinguished by the way in which both fertile and non-fertile stems bear delicate fronds from the nodes of which subsidiary simple fronds depend, so that the whole appearance is of almost magical tracery "created by fairies for their especial use and pleasure" (Newman, 1844).
It grows to a height of about 60 cm from a creeping rhizome, is a muted grass-green in colour and although the stem is grooved like other horsetails it is rather less coarse. The stem has 10 - 18 ridges, each topped by a slight hollow, and the central hollow tube is up to one-third the diameter. The sheath teeth have a thin, dark central stripe flanked by paler margins. Fortunately, this graceful plant is "once-seen, never forgotten".
Wood Horsetail is mentioned at this point in the walk as it was formerly to be seen hereabouts. If not, it can be readily seen in the roadside ditch west of the Black Gate, just west of the first passing place. Returning now towards the path, one passes a small stand of bracken:
Common Bracken. Pteridium aquilinum . From the Greek root pteron ("wing") the full name means "Eagle's Wing" and is said to refer to the way in which the young plant unfurls in stages, so that at one point two outstretched "wings" are topped by the upper crosier and resemble an alighting bird of prey. More obviously, when viewed from below and against the sky, a mature stem looks like a group of soaring eagles in line-astern.
Bracken is common throughout the world and can develop into a monoculture, especially across former habitation or cultivation sites. In many areas it is now regarded as a problem plant, although it was formerly valued as a source of potash, for use as bedding or thatching material, and as packing material. It is highly efficacious in protecting potato clamps, and it is said to assist strawberry crops when spread below the growing fruits; it contains various insect-resistant poisons and was used as a floor-covering by Roman troops stationed along Hadrian's Wall. It was a valuable export, as from 18th c. Jura, until over-exploitation so reduced the resource as to allegedly eradicate the supply. Although the fiddleheads are a delicacy in Japan, Korea and parts of USA, the plant is carcinogenic; the various poisons that it contains include Prussic Acid and although it is resistant to attack by most predators it is a haunt of ticks (beware Lyme's Disease) and also secretes a sugary substance that attracts ants. It can be poisonous to animals, particularly horses.
Bracken is too well known to need description but perhaps it is worth mentioning that it spreads via its rhizome, which is deep, difficult to eradicate and which provides a food store for the plant during winter dormancy. The sori should be found along the edges of the fertile fronds, protected by a false indusium (a curled edge to the frond); but spores do not seem to be produced every year and were not noted in Colonsay in 2015.
Until recently bracken was subjected to poisoning by Asulam (often by helicopter and without prior notice), but this has now been banned, not least because it affected all other ferns as well. Control is possible by rolling and bruising, by appropriate stock management or by cutting. In the latter case, a heavy infestation requires cutting three times per season for three consecutive years; subsequent control will include at least annual cutting, possibly in early July - the aim is to starve the rhizome by the prevention of photosynthesis.
Famously, bracken spores or "seeds" were so small as to be invisible, and it was therefore believed that they could convey that gift to humans. It was believed that the spores ripened on St. John's Eve and if gathered at the correct moment could make the bearer invisible. There are two literary references: in Shakespeare's Henry IV part I, Act II, Scene I where Gadshill declares "We have the receipt (recipe) of fern seed - we walk invisible"; and in The New Inn , where Ben Jonson writes "I had no medicine, Sir, to walk invisible, no fern seed in my pocket".
Continuing along the Ring Circuit, the path turns down towards the left emerging slightly west of Avenue Cottage. Unless intending to visit Druim Buiteachan or A' Choille Mhór, turn left along the avenue. After 50 metres (opposite the original entrance to Colonsay House) there is a prominent Scaly Male Fern, which is magnificent in summer, but which dies back entirely in winter.
Narrow Scaly Male. Dryopteris affinis cambrensis. This plant resembles the specimen that was encountered near the tree-fern and they both are known to die back completely over the winter. They have the distinctive "black spot" and can be seen to have "firm, slightly glossy" fronds and "gold or reddish gold" fairly dense scales. The pinnae are "angled to the plane" like half-opened Venetian blinds, and the pinnules have "rounded-lobed" sides, the basal lobes being "conspicuous and rounded". One needs to check if the indusia are tall, with thin edges, forming a piecrust that splits radially - on balance, both specimens seem likely to be Dryopteris affinis cambrensis, Narrow Male-fern.
Continue along the avenue, noticing some good examples of Common Polypody along the top of the wall on the right, and one or two nice Scaly males beside the ditch. On the wall, one may well notice the distinctive Maidenhair Spleenwort.
Maidenhair Spleenwort. Asplenium trichomanes . The species name, trichomanes, refers to the denuded rachi of old growth and means "bristle hair"; oddly enough the full traditional name was "English Mayden's hair", which seems a little harsh. There are reputedly two forms in Colonsay, but the most common subspecies is the lime-loving Common Maidenhair Spleenwort A. trichomanes subsp. quadrivalens (four sided pinnule). By contrast, Delicate Maidenhair Spleenwort A. trichomanes subsp. trichomanes does not like lime and is said to have a more tufted habit.
This very common and attractive fern has a wiry brown rachis (15 - 20cm) bearing close-placed and often-opposing oblong green pinnae. It has a short, creeping, stocky rhizome (5cm). It is an evergreen, with the old rachis of earlier seasons persisting as a wiry backdrop. The sori are visible in lines at first, with a delicate indusium, but they develop to cover the whole underside of the pinnae in a dense brown mass of spores.
Maidenhair Spleenwort is said to have been used medicinally as an infusion for coughs, also during menstruation and as a laxative.
At the bottom of the slope, just before the bridge, turn left along the path ("Burnside").
Hard Fern. Blechnum spicant . The word "blechnum" is a Greek word for a fern and the "spicant" part of the bi-nomial presumably relates to the "spiky" fertile fronds, which are almost skeletal and earned the plant such common names as "ladder fern" and "herring-bone fern". (As it happens there is another plant beside this path that resembles Hard Fern writ large, Blechnum cordatum, which is an exotic form from South America.)
Hard Fern is an evergreen plant and the barren fronds form a more-or-less prostrate rosette, whilst the fertile fronds stand erect, very much more delicate and very much more spare, genuinely reminiscent of the bones from a filleted fish. The fertile fronds have a stipe running to about half the length, bearing short scales; the frond is pinnate and the linear sori are protected by indusia and very nearly cover the whole underside of the pinnae. In winter, only the evergreen sterile fronds may be seen, but in sheltered places the remnant of the fertile frond survives as a delicate, faded adornment, like Miss Havisham's dress. The sterile fronds are pinnatifid and have longer, pointed scales and the whole plant is of a dark, shiny green.
This splendid fern will be found all over Colonsay, especially in the more acidic areas. It will be found in the hills, beside the tracks and in the woods; perhaps the most magnificent specimens are to be found in A' Choille Bheag, close to the Balnahard march boundary. It is said to prefer a north-facing aspect.
Greater Hard-fern, Blechnum cordatum . Still known in gardening circles as Blechnum chilense and in vernacular Spanish as Costilla de vaca , meaning "Ribs of a cow", a neatly scaled-up version of the British vernacular name of "herring-bone fern" for its counterpart.
Obviously an exotic, one which thrives across a wide altitude range in its native Chile, the infertile leaves are winter-hardy and the plant can survive frosts of more than 10 degrees Celsius in UK. It has become naturalised in parts of Britain and is recorded in the wild from upwards of thirty sites.
Royal Fern. Osmunda regalis . Opinion is divided and there are various theories but it seems reasonable to imagine that the name refers to the 8th century King Osmund of Sussex, who is mentioned in the Anglo Saxon Chronicles and whose position was usurped by King Offa; the impressive fertile fronds might be seen to resemble a staff of authority. Another suggestion is that it was a sovereign remedy in the treatment of fractured bones ("os" = bone, "munda" = cure), since it was regarded as being "... singular good against bruises and bones broken or out of joint"; such use continued until modern times in Cantabria, Spain. It is recorded that the root was used as a starch for linen, also more worryingly it is still suggested as a base for the cultivation of epiphytic orchids. Royal Fern is a protected species, and has been especially vulnerable to plant collectors - which seems odd, since it can easily be raised from a spore. There are many fine examples beside the road to the Strand, as it passes down An Gleann.
The fronds appear in late spring (mid-May onwards) and at first are a quite distinctive shade of pale green, upon a reddish stipe. In due course both stipe and frond turn to a deeper green, but it remains a simple matter to distinguish Osmunda Regalis by colour alone, even from a distance. Fronds are erect, lanceolate, twice pinnate, and can be up to 3m long, growing from a crown or shuttlecock rootstock which, over many years, may become much more than a metre across. The upper pinnae of the fertile fronds are covered with luxurious clusters of russet-brown sori, almost as if the plant is flowering. The mature spores are short-lived, so if gathered should be planted up in sterile peat without delay.
The path leads to the Mill Pond, where one turns right, then right again to follow the route of the mediaeval mill-race (the old mill remained in use until the 1870s). Before leaving the Mill Pond, notice the Water Horsetail:
Water Horsetail, Equisetum fluviatile . Horsetails are true members of the Fern family and in the Carboniferous period (300 - 360 m.y.a) their ancestors, the Calamites, grew to over 30 metres in height; over tens of millions of years they matured, died, were crushed by new growth and became the basis of our coal seams.
Water Horsetail grows in some abundance at this spot, up to almost 2 m. in height, with slender reed-like stems that are notable hollow. There are few whorls of branches and the terminal spore-bearing cones are black in colour. The distinguishing features are "tall, slender, pencil-thick reed-like stems... which snap readily if sharply bent, revealing a very large central hollow" (C.N.Page).
The old mill-race seems as if it should repay careful examination, as the path winds round towards the left where it passes a more open rock-face. In a slightly open area, some 14 paces BEFORE a metal-plate bridge, there is an unusual garden escape 10 cm from the right-hand edge of the path.
Krauss's Clubmoss, Selaginella kraussiana . The native species in Colonsay, Lesser Clubmoss, Selaginella selaginoides , may be readily found elsewhere in Colonsay but Dr. Richard Gulliver of Islay has kindly pointed out this interesting exotic, a native of the Azores and certain parts of south and east Africa. It was apparently introduced to UK in 1878 but by 1917 had been recorded in the wild in both Leitrim and Cornwall. In New Zealand it is listed as an invasive species and in certain conditions can proliferate and form dense mats. It survives temperatures down to minus 5 degrees Celsius.
Continue along the path to rejoin the avenue, and turn left. There are a few ferns to be seen on the masonry beside the gate into the walled-garden, after which one might continue in the same direction by following the path that meanders beside the Mill Pond. Passing through the gate at Pondside Cottage, the garden wall on the left is host to both Common Polypody and Maidenhair Spleenwort. As one walks on along the track, notice another horsetail on the right:
Field Horsetail. Equisetum arvense . Field Horsetail E. arvense is the most common species and is frequently found in waste ground and old gardens. It has long dark brown underground rhizomes that seem to be easily dug up and removed, but which are actually rather persistent. The rhizomes develop numerous little tubers which are easily detached and which form new and independent plants; since the rhizomes run to a great depth (well over 3 metres) it is probably best to learn to live with this very ancient and well-adapted form of plant life.
Typically, horsetails have almost vestigial fronds, reflecting their "primitive" status, and these grow radially from an upright, jointed stem (prone to be pulled apart into sections by small children). At each node there is a sheath to clench the next section and the fronds are set just below the sheath. The sheath consists of a number of teeth, usually to match the number of very distinctive grooves that run vertically the length of the stem.
In the case of Field Horsetail E. arvense, one will find that the length of the first segment of the frond will be a little longer than the teeth of the sheath when held alongside. Other diagnostic features are the cross-section of the hollow stem, and the teeth of the sheaths. It grows to about 90 cm., the fronds point strongly upwards, the stem feels firm, it has between 8 and 20 ridges and the central hollow tube is less than half the diameter.
An interesting feature of Field Horsetail is that it can be mistaken for two different plants. The fertile stems appear in early spring, having no fronds, and being a rather dull brown; they grow quite quickly, producing an apical cone of sporangiophores (multiple sporangia-containers), then shed their spores and die back, to be replaced by the rather different green stems and fronds with which we are more familiar. Remarkably, the spores are equipped with tiny wings called elaters, which are very sensitive to moisture - when they are dry they spring out and launch the spore, helping to keep it aloft , but humidity will cause them to retract and perhaps help to guide their cargo into a suitably damp landing-place.
We have reached the end of the woodland walk, but it seems a pity to miss Colonsay's fourth Horsetail, which can be seen in Kilchattan just opposite the junction with the track to Gortain.
Marsh Horsetail. Equisetum palustre . This too is winter-deciduous, it forms very large colonies in a suitable environment, and is of medium size (ca. 1.5 m. in height). Its whorls of branches are rather coarse, pronouncedly upwardly angled and frequently bearing terminal green or darker cones. Unlike E. arvense , the first segment of the frond is always much shorter than the adjacent sheath and the basal scales are always dark-coloured. At the internodes of the main stem, the central canal or tube will be found to be the smallest of all the horsetails, and the internodes themselves are very smooth. The sheaths at each internode of the main stem end in narrow, back, triangular teeth "each with conspicuous, broad, white margins ... in the shape of a gothic arch" (C.N.Page).
Additional ferns to be seen on longer walks in Colonsay:
On a longer walk, up to half a dozen additional ferns might be seen, and these are noted below but in no particular order:
Hay-scented Buckler-fern . Dryopteris aemula . As has been noted, Dryopteris indicates a woodland genus, and in this context aemula seems to mean "strives to excel", and it is certainly one to notice. It is a relatively small fern, which seems to fight above its weight and does add much beauty to the mosses and other small plants of its habitat.
The erect rhizome is quite small (4 - 5 cm) and the plant, thriving mostly in sheltered locations, is usually enhanced by the remnants of dead fronds. The young fronds are said to have "the lovely scent of new-mown hay", although few people seem to detect it. The developed fronds are up to about 50cm in length, including a stipe of about 20cm, the stipe being of a dark, mat-finish hue and fairly-well endowed with brown scales that do NOT have the darker strip seen in the Broad Buckler species. Both surfaces of the frond have numerous tiny glands, which when touched release the reputed scent of hay. The Hay Scented Buckler Fern is bipinnate (tripinnate towards the base of the rachis)and the pinnae have toothed margins and are concave , described as distinctly "crisped" or "crimped" ; this last feature is easily recognised and rather helpful. The sori are covered by kidney-shaped indusia.
This fern is quite widespread in Colonsay, especially on protected banks in woodlands or under overhangs along north-facing outcrops. In Colonsay's mild climate it may be seen throughout the winter.
Tunbridge Filmy Fern . Hymenophyllum tunbrigense . From the Greek, hymen : a membrane and phyllon : a leaf. Thus "the translucent-leafed fern originally noted at Tunbridge".
The filmy-ferns are especially delicate and attractive, and persist throughout the winter in Colonsay. They look a little like a moss, and tend to grow in the same sort of place, damp rockfaces, sheltered tree-bases etc., usually in a vertical position. The pinnate fronds are membrane-like because they are essentially only as thick as a single cell and the pinnae, spreading out like the wings of an insect or a sycamore fruit, are pinnatifid and centred upon a thicker rachis. Obvious veins along the pinnae look like a very basic road-map and the sori is within a tiny round toothed indusium at the junction of the pinnae with the rachis. The fronds are from 2.5 cm to 7.5 cm and in the case of H. tunbrigense are green with a distinctive olive-brown tint.
Wilson's Filmy Fern . Hymenophyllum wilsonii . This is "the translucent-leafed fern described by Wilson". William Wilson found it growing near to "the far more elegant" H. Tunbrigense in Killarney leading to its initial definitive publication by Sir William Hooker in 1830. It had been first suspected by 1691, from observations in Westmoreland, but confirmation was long delayed.
At first glance, H. wilsonii is very similar to H. tunbrigense but is apparently able to cope with bleaker and less sheltered positions and in fact grows opportunistically in appropriate conditions across four or five years. On closer examination, the fronds of H. wilsonii are seen to be considerably less-divided, and they are also less symmetrical, insofar as to be longer and more concentrated on the upper side. The fronds are of a deeper green, rather darker, and the untoothed sori are pear-shaped, obtruding from the plane of the frond.
Sweet Mountain or Lemon-scented Fern . Oreopteris limbosperma . From the Greek, oros : of the hills, pteris : a fern, limbospermum : having sori on the margin.
This fern requires a flow of water, especially in the growing season, hence is found in areas of high rainfall or on wooded hillside draining slopes and along the sides of burns. It favours acidic, peaty water and is associated with "a light open canopy, mainly Birch ( Betula ) and Rowan ( Sorbus )". It is not winter hardy, but in springtime the fronds grow in a tuft from the stout, erect 10 - 15 cm rhizome and attain a length that may vary greatly according to habitat, from 20cm to as much as maybe 90cm in extreme cases.
So, a "moderate to large-sized fern with ascending, pale bright green , pinnate-pinnatifid fronds, with an outline tapering steadily almost to the very base, arising in distinct shuttlecock-like clusters" (C.N.Page). The pinnate frond is lanceolate, and tapers at both ends, whilst the most useful distinguishing feature may be found on the underside of the lanceolate pinnae, which are arranged in opposite pairs, markedly pinnatifid at the base but only in a vestigial sense as they near the tips. The pinnae extend to a graceful point near tip, but the pinnules are more rounded closer to the rachis, and on the underside the sori are very neatly arranged as fringe around the edge of the pinnules of the pinnae approaching the apex of the frond.
Supposedly the fronds give off a lemon scent when touched; the sori are round rather than kidney-shaped, lacking obvious indusial.
Black Spleenwort. Asplenium adiantum-nigrum . The qualifier, "adiantum", means "water-repellent" and must refer to the shiny or glossy nature of the upper surface of the frond.
The fronds grow in a tuft from a short, creeping rhizome, often only 10 - 25 cm long in Colonsay due to exposure, but there are very sturdy examples of up to 50 cm in favoured locations. The distinctive frond is basically triangular, shiny and of a deep mid-green hue. The pinnae may amount to 15 pairs, and the overall shape is reminiscent of a builder's trowel. The stipe is dark, being black or dark red-brown, shiny and without hairs. The scales on the rhizome are narrow, lanceolate and are darker towards the middle; the fronds persist throughout the winter. The sori trace the midrib of the lateral veins, and are protected by a linear indusium.
Black Spleenwort is found on base-rich rocks, cliffs etc., and can also be found on mortared walls, but apparently it avoids acidic rocks.
Beech Fern. Phegopteris connectilis . The genus is named from a Greek root ("phagos") and might translate as either Beech fern or Oak fern; the word "connectilis" is not obvious.
A very attractive fern, instantly recognisable by the way in which the lowest pair of pinnae are "deflexed"; they thrust downwards away from the rest of the frond, and also upwards, proud of the plane of the blade by about 30 degrees. This gives the fern a very perky, jaunty jizz, which is enhanced by its being a cheerful shade of light green. Sadly, it is not very common in Colonsay, although elsewhere in Scotland it can be quite plentiful in moist and shaded banks in mixed woodland; it may also be found in patches below cliffs and rocky slopes. The fronds are not winter-hardy.
The frond is triangular, ca. 15 - 40 cm long, once-pinnate and pinnatifid, with a slight but noticeable covering of downy-hair on both surfaces. The pinnae are lanceolate and the upper ones are adnate (a pinnule is attached to the rachis). The stipe is noticeably long, up to two-thirds the lengthy of the frond, and the plant produces only a few fronds from its rather slender, creeping rhizome. The sori are round, without an indusium, and are close to the margin of the pinnules.
Sea Spleenwort. Asplenium marinum . The binomial is attributable to Linnaeus in 1753, but it was noted in Cornwall by L'Obel ca. 1571, and illustrated by him in a publication of 1581.
C.N.Page describes it as "A small to medium-sized, robust winter-green fern with distinctive, coarsely divided thick, fleshy shining fronds, growing very near to the sea"; in fact, usually so near as to be very definitely affected by wind-borne spray.
Fronds arise in a tuft and are typically from 15 - 20 cm long, lanceolate, pinnate or pinnately lobed, on a short stout stipe one third the length of the rachis. The pinnae tend to be asymmetric, having a lobe or thumb on the upper side near the rachis. The upper side of the mature frond is a darker, deeper glossier colour than the underside. Sori are readily observed, in lines as with other Asplenium species, and the plant grows from a short ascending rhizome which is covered in dark purple-brown narrowly triangular scales, secured by tough wiry roots deep into the rock crevices. Traditional uses included the treatment of burns.
Other ferns to be seen in Colonsay:
Some ferns and "allies" seen by Kevin Byrne in Colonsay but not yet noticed on these particular walks:
Ferns and "allies" recorded locally but not yet recognised in Colonsay by Kevin Byrne:
Contact: Kevin and Christa Byrne Tel: 01951 200320 or 200242
K & C Byrne Partnership, Homefield, Isle of Colonsay, Argyll PA61 7YR