Aconitum napellus

Taxonomy 

Monk’s-hood, Aconitum napellus L., is a very variable species, with numerous subspecies described in Europe (Tutin et al. 1993). British plants are A. napellus ssp. napellus which has, in the past, sometimes been treated as a separate species, A. anglicum Stapf.

Chromosome No.: 2n = 32 (Stace 2010). 

Aconitum napellus

Photograph: M. Duffell

 

Identification 

Most of the Monk’s-hood plants in Britain are believed to be of garden origin, and these are usually not A. napellus, but a hybrid with the closely-related southern European species A. variegatum. The cross is called A. x cammarum, Hybrid (or Garden) Monk’s-hood. Separating true Monk’s-hood from Garden Monk’s-hood is not always easy, especially as the former is sometimes also cultivated in gardens. A useful key to their identification is given by Silverside in Plant Crib. It can be downloaded here:-gt;> Silverside’s Key pdf, 183 kb).

Distribution 

Aconitum napellus ssp. napellus is thought to be restricted to SW Britain but it is occasionally introduced elsewhere in the British Isles. However, the Maps Scheme maps show the distribution of A. napellus sens. lat., which includes A. x cammarum. Outside Britain, A. napellus ssp. napellus is sometimes described as occurring in parts of France, but this is uncertain (Stace, 1997).

BSBI Hectad Map 

Click on the map to view full-size on the BSBI Maps Scheme website.

Ecology 

It is a tuberous perennial occurring in shady places by streams particularly in wet alder, hazel and oak woodland, usually referable to W6 Alnus glutinosa woodland. In my studies of populations in Shropshire (Duffell 2009) I found that, unlike the garden escapes, the native populations were clearly reproducing sexually, often forming large colonies (thousands of plants), only rarely as single plants.

Status 

Origin: almost certainly native. Although it has always been cultivated as a powerful medicinal herb, there are pollen records that show that an Aconitum species was present in Britain many thousands of years ago (Brayshay & Dinnin, 1999).

Rarity: the native plant is thought to be Nationally Scarce in Britain (Stewart, Pearman & Preston 1994) as it is probably present in fewer than 100 hectads (10 km squares). However, it is considered to be over-recorded in the Welsh Marches (Preston, Pearman & Dines 2002) so possibly it is rarer than that.

Threat: given the quality of the records, it is impossible to give a good estimation of its threat status, but in the New Atlas it is given a Change Index of +1.42 whereas Cheffings & Farrell (2005) put it on their ‘Waiting List’ pending taxonomic studies.

Conservation: no county recorder has yet listed it as an axiophyte, possibly because of the confusion between the taxa. However, its ecology (see below) suggests that native populations should indeed be considered of conservation importance.

Further Work 

We need to review records of A. napellus sens. lat. to see if it is possible to separate the two taxa and produce more helpful maps. It would also be useful to know where A. napellus ssp. napellus is native and where it is only present as a garden escape. Studies into its ecology might also be valuable in determining it conservation importance. Are native populations entirely restricted to W6, for instance? Anyone recording Monk’s-hood in future should collect sufficient material for confirmation, or at least take good-quality photographs of the flowers. I would be happy to look at specimens or photos: email duffell@bsbi.org.uk.

References 
  • Brayshay, B.A. and Dinnin, M. 1999. Integrated palaeoecological evidence for biodiversity at the floodplain-forest margin. Journal of Biogeography 26, 115-131.
  • Duffell, M.S. 2009. The distribution and native status of Monkshood, Aconitum napellus L., in Shropshire. Msc dissertation, School of Biosciences, University of Birmingham.
Citation 
Duffell, M.S. (Date accessed). Species account: Aconitum napellus. Botanical Society of the British Isles, www.bsbi.org.uk.

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