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Botrychium lunaria (L.) Sw., Moonwort

Account Summary

Native, very rare, probably only casual. Circumpolar boreo-temperate; also scattered in the S Hemisphere.

1901; West, W.; Knockmore Hill.

June and July.

Growth form and preferred habitats

Moonwort is a small, rather fleshy, hairless, perennial but deciduous fern that typically grows on near-neutral to strongly basic soils. On ericaceous heaths, B. lunaria is limited to ground which contains at least a little lime and where the dominant subshrubs, Calluna and Erica are absent. B. lunaria usually occurs as scattered individual shoots in short, grassy turf. It is a small plant, the sterile frond rarely being more than 15 cm in height and often only half or one third of this figure, so it is very easily overlooked. The sterile fronds appear in early May, each followed by the adjacent but separate fertile frond. When the latter is eventually fully developed in mid-June, it is somewhat taller than the sterile branch and bears a pinnately divided, triangular spike of globular orange-brown spore-sacs, aptly likened to a miniature bunch of grapes (Page 1997). This is alluded to in the genus name, see below.

Fermanagh occurrence

The local Victorian field botanists West, Abraham and McCullagh all saw this little fern in Fermanagh around the 1900s, as did Meikle and his co-workers in the 1940s. Yet despite all the surveys of the last 30 years, Moonwort has only been seen on four occasions recently, a fact that is difficult to understand as the vegetation at the plant's original sites at Belmore Mountain (recorded in 1946) and Drumkeenagh (recorded in 1902), have probably not changed much during the whole of the 20th century (Revised Typescript Flora, Meikle et al. 1975). The map shows records occurring in seven scattered tetrads, four of them with post-1975 dates. None of the records give information on the species degree of presence, but we recollect that the Legacurragh discovery was a single very small plant, and the latest late-June 2013 record at Doagh Lough was a solitary plant just 3 cm in height.

Details of the other seven Fermanagh records are: Drumkeenagh, near Black River, 1902, J.T. Abraham & F.R. McCullagh; Belmore Mountain, July 1946, MCM & D; scree slope above Doagh Lough, 1947, MCM & D; Callow, Monawilkin, 11 July 1985, ASSI Team, DOENI; Legacurragh, above Florencecourt, 1991, M. Tickner; Isle Namanfin, Lower Lough Erne, 1990-5, D. Hughes; limestone hill south of Dough Lough, 27 June 2013, H. Northridge.

Irish occurrence

In Ireland, while B. lunaria has been found at least once in all but two of the 40 VCs (Scannell & Synnott 1987), it appears to occur only rarely and fleetingly in small numbers as a casual species on dry heathy grassland, mountain ledges and in old lawns or sand-dunes (Webb & Scannell 1983; Webb et al. 1996). The New Atlas hectad map indicates how very scarce B. lunaria has become in Ireland: the map displays scattered modern records in just 14 VCs (28 hectads), mainly in the north of the island.

It could be that unlike earlier generations, modern field botanists do not have an eye for the plant, but more likely it really has declined or become even more transient than previously was the case. RSF is very familiar with Moonwort from continental field trips, but he has never found an original site for the fern in Fermanagh, which does suggest genuine rarity.

In Co Dublin (H21), B. lunaria was already a rare species at the turn of the 19th century, whereas formerly it was more common in upland, usually base-poor pastures. There are only three modern records in Co Dublin: one site with a solitary plant and another with only four individuals. Both the mentioned sites are in unimproved pasture, but interestingly, the third Co Dublin site is from an unusual habitat, in woodland beside a reservoir (Doogue et al. 1998).

British occurrence

In Britain, Moonwort is widely scattered, but while it is predominantly a northern and upland species, it also occurs in a wide range of open, exposed, short-grassland habitats, including at low altitudes sand-dunes, golf-links, old unimproved meadows (now an exceedingly rare habitat), grassy banks and downs. Upland habitats in Britain include grassy moors and heaths, old stabilised grassy screes, alpine meadows and pastures, as well as on cliff ledges (Page 1997).

B. lunaria has suffered a gradual decline in Britain as well as in Ireland as evidenced, for instance, by the map in the Atlas of Ferns (Jermy et al. 1978), where the number of pre-1930 stations recorded almost matches those more recently recorded. The New Atlas hectad map confirms the continuing decline of Moonwort sites in Britain, although often being very small and either solitary or in small populations, it could well be overlooked and under-recorded (A.C. Jermy, in: Preston et al. 2002).

One reason why B. lunaria might fare less well in Irish conditions may be the tendency for it to occur in conditions of high rainfall on very shallow peaty soils formed over limestone. English experience, on the other hand, suggests growth of the fern really benefits from deep, well-aerated soils which allow adequate scope for its deeply running root system and which presumably facilitate the success of the associated mycorrhizal fungi (Page 1997).

European and world occurrence

Beyond our shores B. lunaria is widespread in N, C & S Europe, extending well into the arctic region and as far south as Sicily and the Greek Peloponnese. The distribution peters out in much of W France and in the southern parts of the Iberian Peninsula (Jalas & Suominen 1972, Map 44).

B. lunaria, taken in a broad taxonomic sense, extends in a circumpolar temperate manner around northern latitudes through Asia to Japan, and across northern N America from Alaska to Labrador and on to S Greenland and Iceland. A typical form of B. lunaria occurs also in southern S America along with closely related varieties, and it is also found in SE Australia, Tasmania and New Zealand (Hultén 1962, Map 103; Hultén & Fries 1986, Map 23).

Folklore and medicinal use

Moonwort has long had a reputation for being sporadic in making its appearances and disappearances and, perhaps partly for this reason, it has gathered a considerable body of folklore around it. Magical properties include the ability to unlock locks and unshoe horses' feet. The former notion perhaps derived from the key-like outline of the sterile frond, the latter maybe somehow too associated with its power over iron locks (Step & Jackson 1945; Page 1997). Other well known myths describe Moonwort's powers of alchemy and witches collecting it by moonlight for their magic spells.

In herbal medicine, it was said to heal wounds like Ophioglossum vulgatum (Adder's-tongue) (Grieve 1931). The significant weight of folklore that exists suggests that this small fern was once much more prevalent than now. It was widely known by country people, compared to the few who might recognise it today (Page 1988, 1997).

Names

'Botrychium', which is a diminutive based on the Greek 'botrys', meaning 'a bunch of grapes' (Gilbert-Carter 1964). The specific epithet 'lunaria' is derived from the Latin 'luna' meaning the moon, the curved individual lobes of the sterile frond being likened to the crescent moon (Gilbert-Carter 1964; see also figure in Arber 1970, p. 257).

'Moonwort' is the general widely accepted English common name of the fern, a translation of its specific epithet, but also linked to the magical folklore attached to the plant. Other common names include 'Lunary' or 'Lunarie' (Turner 1568), 'Unshoe the Horse' (Culpeper 1653) and 'Shoeless Horse', another reminder of the folklore (Britten & Holland 1886).

Threats

Improvement of upland pastures for agriculture.