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Ferns of Colonsay - the basic walk Colonsay House Gardens

The 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.

Lady Fern. Athyrium felix-femina . 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). It is not winter hardy, so in January the site of this particular specimen is bare, but although Athyrium felix-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 very 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.

Beware of confusion with Dryopteris filix-mas , D. affinis agg. or D. dilitata.

At the top of the brae (20 metres) turn right and examine the stone gate pier for Polypody and Wall Rue.

Common Polypody. Polypodium vulgare . 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). Colonsay has two recorded species, the other being Intermediate Polypody or Polypodium interjectum .

It 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 hair-like fibrillae. 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 australe , which has linear sori; its most northerly outpost is in Lismore by Oban, and P. interjectum is the hybrid form between P. vulgare and P. australe .

Wall Rue. Asplenium ruta-muraria . The genus Asplenium includes some 700 species, and the name originates with a Greek physician, Dioscorides (50 – 100 AD) who advocated the use of “spleenwort” in medicine. Colonsay has five species, Wall Rue, Black Spleenwort, Sea Spleenwort, Maidenhair Spleenwort and Hart's-tongue.

Wall Rue is compact, bipinnate and bears an obvious resemblance to the flowering plant, Common Rue ( Ruta graveolens ); 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 pinnae 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 e.g. some examples at Oransay Priory. [Also to be seen on wall between Colonsay House carpark and the Tea-Room.]

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 a nice example of Common Polypody on top of the wall to your left - 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 lefthand side, at the foot of a low wall, a small Hart's-tongue Fern.

Hart's-tongue Fern. Asplenium scolopendrium . 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, meaning “millipede”. In this case it is thought to refer to the very distinctive linear sori on the undersides of the frond, resembling just such an invertebrate.

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.

Walk on for a few paces, passing a set of steps on your left, and you will see numerous other examples of this species, some of which are well developed; a few plants in this area have a frond which is divided at its apex, 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 is 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 you will see a particularly healthy epiphytic Common Polypody growing on the base of a tree. Just 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 meaning “oak fern” but more usefully seen as referring to “ferns of the woods”. 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 D. affinis affinis , D. affinis borreri and D. affinis cambrensis . (The common names created for them are Western Golden-scaled Male, Borrer's Scaly Male and Narrow Scaly Male.)They are apomictic (reproduce asexually), and each spore has the same number of spores 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 the non-specialist will normally record the complex as a single species, Dryopteris affinis agg.

As a matter of interest, some of the distinguishing features are tabled here:

As a “species” the Scaly Male Ferns are quite common in Colonsay. They are very similar to a 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 a 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 example is Dryopteris affinis borreri 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 "ordinary" Male Fern - plentiful in this area, e.g. close to the steps at the wall bordering the avenue, but it seems to appear a little later than the "Scaly Males" or the Lady Fern.

Male Fern. Dryopters filix-mas . The species name is Latin, meaning simply “male fern” and the name 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 in fact they are of 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 a nd even-sided, but slightly toothed at the edges which may be slightly 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 and falls away at spore maturity.

Supposedly a cure for tapeworm, apparently Louis XVI paid 16,000 francs to one Mme. Nouffer for such a remedy, details of which had been handed down from the time of Dioscorides, the 1 st c. Greek botanist; it was still regarded as efficacious by 19 th c. medical opinion in Scotlland. Tragus (Hieronymous Bock, 16 th c.) maintained that a piece of the rhizome would cure a sick horse if placed under the tongue; 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 linenen. “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.

Turning back towards the steps, in a few paces one passes to the left of 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”, and referring to the frond, which is like a shield or “buckler”. Colonsay has eight species of Dryopteris of which six are fairly common: Broad Buckler Fern, Male Fern, Hay-scented Buckler Fern and (collectively) the three species of Scaly Male Fern.

Broad Buckler is quite common in woodland, especially in damp places – it is a very obvious 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 which will be seen to have a central darker stripe. 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, 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; also known as Swamp Lantern it has been found useful in many ways, not least by bears who eat it as a laxative after a period of hibernation.

Golden-scaled Male Fern, Dryopteris affinis subs. affinis
Having crossed the bridge, follow the path ahead but after a few metres turn right and cross a small ditch to admire a magnificent Scaly Male Fern. It is covered in a wonderfully thick coat of golden scales, and was in excellent condition in mid-January 2016 and subsequently seems to be recovering well from something of a set-back connected with neighbouring drainage work. Note the very form, very glossy fronds, the "flat in the plane" pinnae with "margins unlobed. The writer is reasonably convinced that this is an example of Dryopteris affinnis affinnis, Golden-scaled Male Fern.

The path continues onwards, passing large numbers of long-established ferns on the right, all of which are winter-dormant, revealing well-developed rhizomes. The area includes numerous Broad Buckler Fern and Lady Fern plus a sprinling of Scaly Males (probably Dryopteris affinis subs. borreri). After 150 metres, one comes to a heavy wooden bridge across a burn, with a mature Tree Fern just beyond and on the right.

Soft Tree Fern. Dicksonia Antarctica . This is actually a native of eastern Australia, where it can grow to 15m in height and prefers damp, sheltered woodland and similar habitats. The “trunk” is in fact the erect rhizome, forming the stipe; the canopy may consist of alternate rows of fertile and sterile fronds but apparently not 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 the initial massacre of 1828, so the information comes from indirect sources. It is said that the young crosiers can be consumed as food.

Nearby there is a sSmall and convenient stand of bracken:

Bracken. Pteridium aquilinum . From the Greek root pteron (“wing”) the full name is Eagle's Wing and is probably a reference 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. 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 from 18 th 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; 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”.

Please email corrections, comments, suggestions and additional information to colonsaybyrne@gmail.com