Ophioglossum vulgatum L., Adder's-tongue
Account Summary
Native, occasional. Circumpolar temperate, but widely disjunct in Eurasia, N America and E Asia; also in isolated warmer stations further south.
1860; Smith, Rev Prof R.W.; Ardunshin.
April to September.
Growth form and preferred habitats
As this fern is small and generally occurs as thinly scattered individuals, it is very easily overlooked. It is therefore hard to be certain despite our efforts that O. vulgatum is fully recorded in the county. It needs to be deliberately searched for from late April to September when the annually produced aerial parts of this perennial species are visible. The texture of the sterile frond and the fact that it has no mid-rib, together make it fairly easy to spot once you know the sort of moist, usually calcareous or lime-enriched loamy, clay soil it favours, and 'you've got your eye in for it'!
It does, in fact, occur in a wide variety of calcareous or mildly acidic, moist, unimproved grassland and rocky habitats, including calcareous lakeshores, limestone pavement, scree and sometimes in scrub woodland when it is invading such sites. In our experience, however, it is never really abundant, even on or around grassy turloughs' floors (ie vanishing limestone lakes which drain through their base), which ought to suit its preferences perfectly (Webb & Scannell 1983; Page 1997).
Fermanagh occurrence

In Fermanagh, this little, deciduous, rhizomatous, taxonomically polymorphic fern has been recorded in a total of 64 tetrads, 12.1% of those in the VC. As the distribution map indicates, Adder's-tongue is widely distributed in Fermanagh, mainly to the SW of Lough Erne, but with a few scattered stations further east. The most isolated easterly recent station is on a roadside at Knocknalosset Td, where RHN found it in June 1990.
Vegetative Reproduction
Adder's-tongue is capable of vegetative reproduction, producing shoot buds on its spreading roots, so that patches of the plant may develop over time. Having said this, like Botrychium lunaria (Moonwort), another fern species closely dependant on a mycorrhizal fungal partner in the soil, O. vulgatum population densities fluctuate from year to year, apparently being very sensitive to prevailing local climate (Page 1997).
Irish occurrence
The second edition of the Census Catalogue of the Flora of Ireland indicates that O. vulgatum has been recorded at least once in all 40 Irish VCs (Scannell & Synnott 1987). Careful manual inspection of the Botanical Society Atlas (Perring & Walters 1962, 1987) shows that in many Irish VCs this is literally the case, there being a solitary plotted symbol. On the hectad map of Ireland, 71 of the symbols represent pre-1930 records. While the most recent Irish Flora continues to describe this easily overlooked fern as 'occasional' (Parnell & Curtis 2012), in reality Adder's-tongue is much more scarce and scattered, and in some areas it is in long term decline. On the other hand, Irish field recording has greatly improved over the last 50 years, and the New Atlas hectad map plots 110 Irish hectads with post-1987 records, a high proportion of these being in the northern province of Ulster (Preston et al. 2002).
Population decline
There is evidence of a long term decline of O. vulgatum populations in lowland areas of Britain & Ireland and the trend appears particularly obvious in Ireland. The species losses are widely attributed to drainage, agricultural intensification, a changing grazing pattern and the move from hay to silage production (C. Jermy, in: Preston et al. 2002). At the same time, O. vulgatum seems to be holding its ground in the areas of Fermanagh where agriculture is less intensive, while undoubtedly it is now less frequent in the N & E of the VC, where drainage and disturbance associated with pasture improvement will probably eventually eliminate it entirely. Even in areas 'improved' in this manner, however, the fern may manage to hold on in adjacent, more rocky marginal ground. The decrease in the number of unimproved limestone or lime-enriched pasture sites in Fermanagh is very real, however, a rough measure being given by the fact that there are 15 tetrads where the species was recorded prior to 1976, but has not been re-recorded. This compares with 49 tetrads which have post-1975 records of the fern.
The decline of this species in Ireland appears obvious from the map in The Fern Atlas (Jermy et al. 1978, p. 28), and this has also been commented upon in other modern Irish VC Floras, notably that of Co Dublin (H21), and of the three VCs in NE Ireland (Cos Down, Antrim and Londonderry (H38, H39 & H40) (Doogue et al. 1998; Hackney et al. 1992). However, two recently published Floras from the far south of the island indicate that in the areas covered, Adder's-tongue has either been under-recorded in the past, or has recently increased its presence: in Co Waterford (H6), Green (2008) lists the species from eight sites post-1996 and in Co Limerick (H8), Reynolds (2013) lists six sites with modern records.
British occurrence
O. vulgatum appears much more frequent and widespread in lowland England and S Wales than is the case in Ireland. The New Atlas map, displaying plant data recorded up to the end of 1999, indicates that there has been a considerable improvement in the recording of this fern in Britain over the last 40 years in comparison with the original Botanical Society Atlas (Perring & Walters 1962). However, despite the enhanced recording effort, the presence of O. vulgatum thins and becomes sparse and declining to the N of a line between Morecambe and Middlesbrough (Preston et al 2002; Wardlaw & Leonard 2005). Drainage and the widespread agricultural use of fertiliser and slurry-spreading in particular, have undoubtedly accelerated the previously gradual process of Adder's-tongue population decline, a process which in Britain has been operating for more than three centuries (Page 1997).
European and world occurrence
O. vulgatum is widespread in W & C Europe, becoming more coastal in Scandinavia and very scattered in the Iberian Peninsula and along the N Mediterranean coast (Jalas & Suominen 1972, Map 42). Elsewhere, the species (considered broadly) extends in an extremely widely-spaced, disjointed manner across boreal Asia to Japan, Burma and N America as a very disjunct circumpolar temperate species. It also occurs further south in equatorial W Africa and in Mexico (Hultén 1962, Map 91; Hultén & Fries 1986, Map 21).
Folklore and uses
In earlier centuries Adder's-tongue, like Moonwort, was very much more plentiful in the British Isles, and it was better known than it is today so that it developed a folklore reputation. It was regarded both as a herbal antidote for snakebite from Adders (another case of 'the Doctrine of Signatures' based on a fanciful resemblance), and as having a malevolent influence on the health of pasture grasses (Step & Jackson 1945; Page 1997). An ointment called 'Green Oil of Charity' was prepared using the fern and was still in demand as a salve for wounds in the 1940s in parts of Britain (Grieve 1931; Step & Jackson 1945). The expressed juice of the leaves, drunk either alone or with distilled water of Horsetail, was once widely used by country people for internal wounds and bruises, vomiting or bleeding at the mouth or nose (Grieve 1931). On the other hand, doubts as to the authenticity of the reports of folk use of this small, rather scarce native are expressed by Allen & Hatfield (2004), who suspect the possibility of imports of plant material and possible 'borrowings' of reported use from older herbals.
Names
The genus name 'Ophioglossum' is a combination of two Greek words, 'ophis' = a serpent and 'glossa' = a tongue, said to be because of the appearance of the fertile branch, although in reality no snake's tongue has any likeness to it. The Latin specific epithet 'vulgatum' means common or ordinary (Step & Jackson 1945).
Additional English common names locally applied to O. vulgatum (and sometimes also to other unrelated species), include 'Edder's-tongue', 'Serpent's-tongue', 'Dragon's-tongue', 'Adder's Spear', 'Adder's-grass' and 'Cock's-comb' (Britten & Holland 1886).
Threats
Disturbance of older pastures, including drainage, agrichemical application and grazing pressure from sheep and rabbits would all tend to depress the frequency of this small fern.