Aconitum napellus L. s.l., Monk's-hood
Account Summary
Introduction, neophyte, very rare garden escape.
1884; Barrington, R.M.; Castle Hume estate, Lower Lough Erne.
May to July.
Irish status
When it is found in Ireland, which is only rarely the case, A. napellus is always regarded as a naturalised garden escape. The plant generally occurs on roadsides and open areas on field margins.
Fermanagh occurrence
A. napellus s.l. has been recorded in Fermanagh on a total of eight occasions and at only four scattered sites in recent decades. A possible reason for the near disappearance in the 'wild' of this conspicuous, tall, beautiful, blue-flowered garden escape could be its well-known extremely poisonous nature, which may have led to its eradication by landowners when found in order to protect grazing stock.
The details of the other seven Fermanagh records are: Galloon Td, Upper Lough Erne, 1951, MCM & D; Arney village, 1952, MCM & D; Clonelly, NW of Kesh, 25 July 1976, Miss N. Dawson; Colebrooke Church, 1 July 1997 & 24 June 2003, RHN; roadside at Killadeas, near hotel entrance, 24 May 2002, RHN; and roadside at Cornamucklagh Td, NE of Brookeborough, 29 May 2004, RHN.
Growth form and reproduction
Monk's-hood has a blackish tuberous taproot or rootstock as its perennating (ie overwintering) organ, from which arises a usually unbranched flowering stem up to 1.5 m tall, but generally less. The plant has no means of vegetative reproduction and relies entirely on seed for its increase and dispersal. The cowl-hooded or helmet-shaped deep reddish-violet or purplish-blue flowers are produced in a long terminal raceme that may consist of around 30 flowers if the stem is unbranched and up to 100 when branched. The irregular flower conceals two long nectar-secreting spurs inside the hood, which are interpreted either as petals or as staminodes (modified sterile stamens) (Blamey & Grey-Wilson 1989). Each flower contains 3-5 carpels which, after the stigma has been pollinated by long-tongued bumblebees, ripen to form upright, many-seeded follicles.
The seeds are rather large (6 × 3 mm) and they bear three wings, one of which is slightly wider than the others (Butcher 1961; Clapham et al. 1962). The 'wings' are not very large, but they undoubtedly assist the seed to travel slightly further through the air when shaken out of the censer-like fruit. As with Aquilegia vulgaris (Columbine), one would not expect the plant to have great powers of dispersal, yet its occurrence in the wild indicates it is well able to escape from gardens on a regular basis. Apart from this, the reproductive ecology of A. napellus appears a completely closed book. I have not located any information on seed dormancy, longevity or germination.
A supposed native British variant
A form of the plant referred to as A. napellus subsp. napellus (or subsp. anglicum) has traditionally been considered indigenous in S Wales and parts of SW England (Watson 1883; Druce 1932; New Atlas). The semi-native habitats it frequents are characterised by calcareous to slightly acidic soils along stream banks that are often shaded, in damp, open woods or meadows (R.A. Fitzgerald, in: Preston et al. 2002). This supposedly native British population is mapped by Jalas & Suominen (1989, Map 1576), showing in addition to its British distribution a solitary record of a plant of similar form in the Pyrenees.
Since A. napellus has been grown in gardens for centuries and first made a 'wild' appearance in the British flora as late as 1821 (R.A. Fitzgerald, in: Preston et al. 2002), I find it quite amazing that anyone today would simply assume and assert that a species or subspecies is native (and/or endemic) to a region without first making a rigorous objective examination of all the circumstantial evidence that might be assembled to support such a status (Webb 1985; Forbes 2000). The 'endemic native' plant is reputedly found flowering in early summer in shady riverside sites in SW England and S Wales (A.J. Silverside, in: Rich & Jermy 1998).
Aconitum napellus subsp. napellus is distinguished from many of the more widespread garden forms of the plant (which are sometimes of hybrid origin), by having less deeply cut leaves, but with more finely pointed ultimate leaf segments. It also has a slightly earlier flowering period and the helmet of the flower is hemispherical, not elongated (A.J. Silverside, in: Rich & Jermy 1998).
Apart from its taxonomy and alkaloid content, the plant appears little studied and I cannot locate any recent references on its biology or ecology, let alone on its status, apart from the brief treatment by John Akeroyd in Scarce plants in Britain (Stewart et al. 1994).
Irish occurrence
A. napellus s.l. is slightly less rare than elsewhere in Ireland in the six county province of Northern Ireland, where it has records in five counties (the exception is Co Armagh (H37). In the Republic of Ireland, the species has only five widely scattered records (Preston et al. 2002).
British occurrence
In Britain, A. napellus s.l. is widespread throughout as a garden escape, but it has a greater presence in western districts of England and Wales, while north of the Scottish border it becomes somewhat more frequent in eastern areas. It is very possible that some of the mapped plants really are the garden hybrid A. × cammarum L., a cross between A. napellus and A. variegatum (R.A. Fitzgerald, in: Preston et al. 2002).
European occurrence
A. napellus s.l. is a very variable species endemic to W and C Europe, its distribution on the continental mainland extending south to C Spain and stretching eastwards to the Carpathian mountains. It is absent, however, from most of the Mediterranean basin (Jalas & Suominen 1989, Map 1575). The taxonomy of the species (or polymorphic aggregate of forms) is greatly confused by the recognition by some of a range of subspecies (which others elevate to species rank), plus a history of very many name changes. As is the case with Aquilegia vulgaris (Columbine), which sometimes occurs in similar shady and damp habitats to A. napellus, the comparative scarcity of the species and its insect pollination syndrome would hardly lead us to expect the appearance of either its pollen or its seed in the fossil record, and indeed none exists (Godwin 1975).
Toxins
The plant contains a cocktail of at least four alkaloids including aconitine, which even on its own is highly toxic, so that Monk's-hood has the reputation of being the most poisonous plant in the British Isles (Cooper & Johnson 1998, p. 188). Perhaps because its poisonous nature is so well known and hence its subsequent removal from sites where grazing animals might find it, there are very few reports in recent years of animal or human poisoning by the species in these islands.
Names
The genus name 'Aconitum' is Latin and is thought by some to be derived from the Greek name 'Akoniton' (although Gilbert-Carter (1964), for instance, regards the etymology as doubtful). 'Aconitum' is a classical name first given to an unknown poisonous plant by Theophrastus (Gledhill 1985; Stearn 1992) and later reused by the Swedish botanist, Linnaeus, for the current genus. The Latin specific epithet, 'napellus', is a diminutive of 'napus', which means 'little turnip', an obvious allusion to the tuber of the plant (Stearn 1992).
The English common name 'Monk's-hood' was first given by Lyte (1578), who described "The flowers be as little hoodes", translating the name directly from Dutch and German (Grigson 1974). In his excellent The Englishman's Flora, which deserves to be on every Celt's bookshelves too, Grigson (1955, reprinted 1987) remarks that the local names of the garden form of this very poisonous plant are all charmingly innocent. Most of them relate to the odd form of the flowers, "and especially to the fluttering, dove-like nectaries". They include 'Doves in the Ark', 'Lady Lavinia's Dove Carriage'. Many alternative names refer to bonnets, caps, helmets or hoods, for instance, 'Old Woman's Nightcap' and 'Face in Hood' (Britten & Holland 1886).
Fermanagh threats
None, as it is much too rare to be a threat to natural vegetation, or to grazing stock. With its recognised status as a rare, neophyte, garden escape, we are not concerned about threats of any kind to the survival of Aconitum napellus.