Weeding the nettles III: Named nonsense versus named morphotypes in European Urtica dioica L. (Urticaceae)

Urtica dioica L. in its wider sense is reported from nearly all temperate zones of the world, from throughout Eurasia, from North America and South America, from S Africa and New Zealand. In Europe, over 70 infrasubspecific names referable to the widespread and often weedy U. dioica subsp. dioica have been used in one form or another; over 40 of them are formally described. Many of these names are invalid and/or superfluous. However, several identifiable morphotypes can be found, which are stable in cultivation and usually occur in several different regions of Europe and/or are characterized by some type of habitat preference. These morphotypes in their most characteristic expression are quite well differentiated, but are connected by a continuous series of intermediates in nature. As a working hypothesis we here propose the tentative recognition of the following five morphotypes: U. dioica subsp. dioica var. dioica, -var. hispida, -var. sarmatica, -var. holosericea, and -var. glabrata. A characterization of each morphotype and corresponding synonyms are presented here based on extensive field studies, literature and herbarium studies and cultivation of material. Lecto-and neotypes are designated where necessary for some of the more important names.