Urtica cannabina 2 Bergianska, Stockholm 050913 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dioica ssp dioica 2 Lund Sk 121019 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dioica ssp dioica 3 Lund Sk 121019 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dioica ssp dioica var holosericea 1 Saavioja FI 120729 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dioica ssp dioica var holosericea 3 Saavioja FI 120729 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dioica ssp dioica var holosericea 5 Vesterroder SE of Stokkemarke, Lolland DK 130811 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dioica ssp dioica x kioviensis Knudshoved, Själland DK 101003 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dioica ssp sondenii 2 Kvikkjokk, Lule Lappmark 870714 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dubia 2 Magaluf, Mallorca 110422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dubia 3 Magaluf, Mallorca 110422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dubia 5 Magaluf, Mallorca 110422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica ferox 1 Wainuiomata Forest Reserve E of Wellington NZ 151115 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica ferox 10 Wainuiomata Forest Reserve E of Wellington NZ 151115 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica ferox 2 Wainuiomata Forest Reserve E of Wellington NZ 151115 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica ferox 6 Wainuiomata Forest Reserve E of Wellington NZ 151115 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica ferox 7 Wainuiomata Forest Reserve E of Wellington NZ 151115 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica kioviensis 1 Knudshoved, Själland DK 101003 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica kioviensis 2 Knudshoved, Själland DK 101003 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica kioviensis 3 Knudshoved, Själland DK 101003 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica kioviensis 4 Knudshoved, Själland DK 101003 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica kioviensis 6 Knudshoved, Själland DK 101003 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica membranacea 2 Alanya, Turkey 090411 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica membranacea 3 Alanya, Turkey 090411 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica membranacea 6 Torcal de Antequera, Andalucía Spain 220418 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica morifolia 1 Barranco de la Madera 090506 (Richard Åkesson) - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica morifolia 2 Los Tilos from Casa del Monte, LP 090509 (Richard Åkesson) - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica pilulifera 11 Copenhagen Bot Garden 130821 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica pilulifera 12 Kampos, Lesvos, Greece 100512 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica pilulifera 4 Ipsilou, Lesvos, Greece 130507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica pilulifera 5 Ipsilou, Lesvos, Greece 130507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica pilulifera 6 Ipsilou, Lesvos, Greece 130507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica pilulifera 7 Copenhagen Bot Garden 130821 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica pilulifera 8 Copenhagen Bot Garden 130821 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica pilulifera 9 Copenhagen Bot Garden 130821 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica stachyoides 4 E of Icod, Tenerife 160406 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica stachyoides 5 E of Icod, Tenerife 160406 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica stachyoides 6 E of Icod, Tenerife 160406 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica urens 6 Höllviken Sk 130620 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica 1 Santa Margarita River, CA 130415 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica cannabina 1 Bergianska, Stockholm 050913 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dioica ssp dioica 1 Höllviken Sk 120721 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dioica ssp dioica 4 Lund Sk 121019 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dioica ssp dioica 5 Höllviken Sk 120721 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dioica ssp dioica var holosericea 2 Saavioja FI 120729 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dioica ssp dioica var holosericea 4 Vesterroder SE of Stokkemarke, Lolland DK 130811 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dioica ssp sondenii 1 Kvikkjokk, Lule Lappmark 870714 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dubia 1 Magaluf, Mallorca 110422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dubia 4 Magaluf, Mallorca 110422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dubia 6 Magaluf, Mallorca 110422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dubia 7 Magaluf, Mallorca 110422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dubia 8 Magaluf, Mallorca 110422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica dubia 9 Magaluf, Mallorca 110422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica ferox 3 Wainuiomata Forest Reserve E of Wellington NZ 151115 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica ferox 4 Wainuiomata Forest Reserve E of Wellington NZ 151115 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica ferox 5 Wainuiomata Forest Reserve E of Wellington NZ 151115 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica ferox 8 Wainuiomata Forest Reserve E of Wellington NZ 151115 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica ferox 9 Wainuiomata Forest Reserve E of Wellington NZ 151115 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica kioviensis 5 Knudshoved, Själland DK 101003 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica membranacea 1 Alanya, Turkey 090411 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica membranacea 4 Alanya, Turkey 090411 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica membranacea 5 Torcal de Antequera, Andalucía Spain 220418 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica membranacea 7 Torcal de Antequera, Andalucía Spain 220418 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica morifolia 3 N of Portillo de Las Cañadas, Tenerife 970318 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica pilulifera 1 Copenhagen Bot Garden 130821 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica pilulifera 10 Copenhagen Bot Garden 130821 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica pilulifera 2 Ipsilou, Lesvos, Greece 130507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica pilulifera 3 Ipsilou, Lesvos, Greece 130507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica stachyoides 1 Los Silos, Tenerife 160409 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica stachyoides 2 Los Silos, Tenerife 160409 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica stachyoides 3 E of Icod, Tenerife 160406 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica urens 1 Höllviken Sk 130620 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica urens 2 Höllviken Sk 130620 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica urens 3 Höllviken Sk 130620 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica urens 4 Höllviken Sk 130620 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Urtica urens 5 Höllviken Sk 130620 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).