Urtica dioica and U. galeopsifolia

Taxonomy 

The Common, or Stinging Nettle is one of the most well-known plants in Britain. Its scientific name is Urtica dioica L. (syn. U. hispida DC.). There are several other types of nettle in the British Isles, but the only common one is the Annual Nettle U. urens, which is found in arable fields. However, there is also a plant known as Stingless Nettle which is sometimes treated as a subspecies or variety of Common Nettle and sometimes as a species in its own right. This is Urtica galeopsifolia Wierzb. ex Opiz (syn. U. dioica ssp. galeopsifolia (Wierzb. ex Opiz) Chrtek). The existence and distribution of this Stingless Nettle is one of the current topics for research amongst British botanists.

McAllister (1999) counted the chromosomes of nettles in Britain and found U. dioica to be tetraploid (2n = 52), whereas U. galeopsifolia was diploid (2n = 26). Stace (2010) reports 2n = 48, 52 for U. dioica ssp. dioica, and 2n = 26 for U. dioica ssp. galeopsifolia.

 

Urtica dioica Urtica galeopsifolia

Urtica dioica (left) and U. galeopsifolia (right) - note the characteristically narrower leaves of the latter.

Photography: A. Leak (l); A.J. Lockton (r)

Distribution 

Widespread throughout the British Isles, absent only from the highest mountains in Scotland. Its global range includes all of Europe and Asia, and it is naturalised elsewhere in the world. Urtica galeopsifolia is much less well known. In Flora Europaea (Tutin et al. 1993) it is listed for most European countries, but GBIF seems to have no records of it anywhere (as of 2009).

BSBI Hectad Map 

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

Urtica dioica

Urtica galeopsifolia

Ecology 

U. dioica occurs naturally in a wide variety of habitats, from woods to fens. It is even found on dried-out mires and in eutrophic places such as livestock feeding stations on high mountains. It often becomes overwhelmingly abundant beside lowland rivers, where fertilisers and topsoil washed down from farmland create ideal conditions. It is often favoured by eradication programmes for Japanese Knotweed and Himalayan Balsam. U. galeopsifolia is found in wetter conditions and on less fertile soils, typically in alder and willow carr or Phragmites fen. A huge amount of information on the ecology, history and uses of U. dioica has been compiled by Keith G.R. Wheeler in his book A Natural History of Nettles (privately published, 2004).

Status 
  • Origin: native throughout.
  • Rarity: Urtica dioica is common and widespread. U. galeopsifolia is probably under-recorded but is nevertheless much less common; possibly Nationally Scarce (fewer than 100 hectads in Britain) and the equivalent in Ireland.
  • Threat: The New Atlas (Preston, Pearman & Dines 2002) gives U. dioica a small positive Change Index of +0.28 but Leach (op. cit.) suggests that it has increased within its range, which would not show up at the hectad scale. Given the paucity of records of U. galeopsifolia, it is not possible to assess any change.
  • Conservation: many ecologists would consider U. dioica to be something of a cacophyte - an unwanted plant - because highly eutrophic, disturbed habitats are so common. By contrast, U. galeopsifolia occurs in less fertile conditions and may well be an axiophyte, although no counties have yet designated it as such.
Further Work 

The most obvious need is for further studies into the taxonomy and ecology of Urtica galeopsifolia. The Maps Scheme shows it to occur in widely scattered places throughout he British Isles, but there is no obvious pattern to the dots. Intermediates or hybrids between the two species have also been recorded, tentatively with intermediate chromosome numbers. No such taxon has yet been named or formally described. Martin Godfrey researches this taxon and is willing to receive specimens for identification.

References 
  • McAllister, H.A. 1999. Urtica galeopsifolia Wierzb. ex Opiz (Urticaceae) confirmed for Britain by its chromosome number. Watsonia 22, 275-278
Citation 
Lockton, A.J. & Godfrey, M.F. (date accessed). Species account: Urtica dioica. Botanical Society of the British Isles, www.bsbi.org.uk.

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