Lycopodium clavatum L., Stag's-horn Clubmoss

Account Summary

Native, very rare. Circumpolar boreo-temperate.

1905; Colgan, N.; Altscraghy, on Cuilcagh slopes.

Throughout the year.

Growth form and preferred habitats

Unlike H. selago, individuals of Stag's-horn Clubmoss are regarded as being fairly long-lived plants which slowly develop sparse but wide-spreading colonies with long, horizontally running stems, sprawling through or over a mass of accumulated surface leaf and moss litter. The undulating stem, often vivid green in colour, was aptly described by Step and Jackson (1945) as having 'the combined stiffness and pliancy of copper wire'. These spreading stems occasionally branch and root themselves at intervals, anchoring the clone to the substrate. They also send up occasional erect leafy shoots terminating in characteristic, perfectly vertical, bare stalks, on which two or three long, slender cones are borne (Page 1997).

Reproduction

L. clavatum does not produce any 'bulbils' or 'gemmae', but relies entirely on its spores for reproduction, a fact that has probably contributed to its decline to extreme rarity, at least in Ireland. Like H. selago, Stag's-horn Clubmoss is very liable to destruction by fire. Thus the widespread practice of maintaining heather vigour on mountain slopes by the establishment of a cyclical burning regime, has undoubted killed off many local populations, particularly in Scotland and in Ireland where this is a regular form of heath management.

Irish occurrence

While Page (1997) described Stag's-horn Clubmoss as the best known clubmoss in the British Isles, it is much more local in Ireland, indeed rare and declining for at least 60 years. Although it did not fit the criteria for inclusion in the vascular plant Irish Red Data book (Curtis & McGough 1988), L. clavatum features in the list of scarce and threatened vascular plants in the 'Biodiversity in Northern Ireland' discussion document (Brown et al. 1997). The scale of the decline of Stag's-horn Clubmoss in Ireland is demonstrated by the fact that Praeger (1934) listed it as occurring or having occurred in 27 Irish VCs, while Scannell and Synnott (1987) suggest it is still present in just 11 VCs (7 of which were northern and did not include Fermanagh).

The statistics available in the Fern Atlas are telling: of the 62 hectads mapped with records for L. clavatum in Ireland, only 19 have post-1930 symbols (Jermy et al. 1978). The New Atlas of Ferns (2005) confirms the decline, although the map indicates a wider distribution: there now are a total of 81 Irish hectads plotted, 58 of them with pre-1970 records only (Wardlaw & Leonard 2005). The new fern map plots 17 post-1986 hectads in Ireland, all but three in the northern half of the island.

Fermanagh occurrence

L. clavatum was not seen in Fermanagh during the 83 years between Colgan's original find on the slopes of Cuilcagh mountain in 1905 and its discovery by H.J. Northridge in 1988 on a peaty roadside bank on Doon Hill at an altitude of just 250 m. Regrettably, the small population at this new and most unusual lowland site was subsequently destroyed by the unwitting dumping of earth on top of it sometime prior to January 1995. Happily, in April 1995 a third station was discovered by Matthew Tickner on a knoll by a burn flowing through blanket bog on the Pettigo Plateau. Previous to this in January 1990 the species was rediscovered by RHN surviving on Cuilcagh on the slope below the summit cairn, which was very possibly Colgan's original site, bringing the number of extant Fermanagh stations back to two!

The typical habitat of L. clavatum is on N-facing, acidic mountain grasslands or heaths, subject to high rainfall, but where there is sufficient slope to allow drainage water to flush through the ground (Jermy et al. 1978; Page 1997). The Cuilcagh site in Fermanagh exactly fits the typical habitat of L. clavatum, ie N-facing, acidic mountain grassland and heath, subject to high rainfall, but on a slope where drainage water flushes the ground. Plants in the site sprawl in a loosely undulating manner over thin peaty soil, covering hidden boulders amid low-growing heather moorland composed mainly of Erica cinerea (Bell Heather), Calluna vulgaris (Common Heather or Ling), Vaccinium myrtillus (Bilberry) and Empetrum nigrum (Crowberry). Both Huperzia selago (Fir Clubmoss) and Diphasiastrum alpinum (Alpine Clubmoss) also grow near this particular site.

At both its Fermanagh sites L. clavatum is struggling to compete with Calluna. A visit to the Pettigo Plateau station in October 2010 located only two small patches of the clubmoss.

British occurrence

In Britain, L. clavatum is a mainly northern species, but it has more sites in S England than any of the three other clubmoss species with which it most nearly overlaps, Huperzia selago, Diphasiastrum alpinum (Alpine Clubmoss) and Selaginella selaginoides (Lesser Clubmoss)(Jermy et al. 1978).

In Britain and Ireland, and especially in more lowland sites, the species has decreased or disappeared due to the intensification of agriculture and utilisation of previously ignored rough marginal land (Page 1997).

European and world occurrence

Like Huperzia selago (Fir Clubmoss) L. clavatum is a widespread circumpolar species which also extends into the southern hemisphere and worldwide has several named varieties (Hultén 1962). In Europe it displays a mainly western distribution with a relatively continuous range from N Fennoscandia to the Alps and Pyrenees (Jalas & Suominen 1972; Page 1997). In Britain and Ireland it is a mainly northern species, but it has more sites in S England than any of the three other clubmoss species with which it most nearly overlaps, Huperzia selago, Diphasiastrum alpinum (Alpine Clubmoss) and Selaginella selaginoides (Lesser Clubmoss)(Jermy et al. 1978).

Uses

In former years L. clavatum was collected as a source of 'Lycopodium powder', the dry, light, bright yellow spores being used in school physics experiments to display sound waves. The spores were collected commercially chiefly in Russia, Germany and Switzerland in July and August, the cones being cut off and sieved to remove the Lycopodium powder or 'vegetable sulphur', or even 'vegetable brimstone', as it was sometimes referred to (Grieve 1931). The spores, like the rest of the plant, are very flammable, and in years gone by they were used in the manufacture of fireworks and for pyrotechnic stage lighting effects in theatres (Mabberley 1997).

In herbal medicine the spores were used alone (ie apart from the rest of the plant), from the seventeenth century onwards, being employed as 'a diuretic for dropsy, a drastic in diarrhoea, dysentery and suppression of urine, a nervine in spasms and hydrophobia, an aperient in gout and scurvy, a corroborant in rheumatism, and also as an application to wounds' (Grieve 1931). The use of Lycopodium powder was never admitted to the British Pharmacopoeia, but herbalists in the British Isles did use it as a dusting powder for treating skin diseases. The main pharmaceutical use was as a pill powder, to envelope pills and prevent them sticking together when boxed (Grieve 1931). In some rural parts of the British Isles there once was a folk-tradition of using garlands of Stag's-horn Clubmoss for 'personal adornment' in some form of ceremony (Page 1988 & 1997).

Names

The genus name 'Lycopodium' is derived from a combination of two Greek words 'lycos', meaning 'wolf', and 'podion', 'little foot', a translation of the German, 'Wolfsklauen', first used by the German physician and botanist, James Theodore Tabernaemontanus. He fancied that the clubmoss shoot resembled the paw of a wolf in miniature (Gilbert-Carter 1964; Hyam & Pankhurst 1995; Step & Jackson 1945). The specific epithet 'clavatum', is Latin meaning 'club-shaped', which like the general name of the group 'Club-moss', refers to the club-like shape of the fruiting cones (Stearn 1992; Step & Jackson 1945). The English common name 'Stag-horn Clubmoss' is a book name, and alternative local folk names do not appear to exist.

Threats

Overgrazing by sheep, shading overgrowth by Calluna, and fire.