Myriophyllum alterniflorum 1 Bäckhalladalen, Gladsax, Skåne 950610 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum alterniflorum 10 Cloon & Laghtanabba Bog E of Claddaghduff, Ireland 170525 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum alterniflorum 8 Cloon & Laghtanabba Bog E of Claddaghduff, Ireland 170525 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum alterniflorum 9 Cloon & Laghtanabba Bog E of Claddaghduff, Ireland 170525 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum propinquum 1 Baring Head SE of Wellington NZ 151115 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum propinquum 2 Baring Head SE of Wellington NZ 151115 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum sibiricum 1 mouth of lake Limsjön, Leksand, Dalarne 930723 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum sibiricum 2 mouth of lake Limsjön, Leksand, Dalarne 930723 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum sibiricum 3 mouth of lake Limsjön, Leksand, Dalarne 930723 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum sibiricum 5 Lille Saltsö, Kangerlussuaq, Greenland 140704 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum sibiricum 6 Lille Saltsö, Kangerlussuaq, Greenland 140704 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum sibiricum 7 Lille Saltsö, Kangerlussuaq, Greenland 140704 - Photo: (© 2014 Jan Thomas Johansson).

Myriophyllum sibiricum 8 Lille Saltsö, Kangerlussuaq, Greenland 140704 - Photo: (© 2014 Jan Thomas Johansson).

Myriophyllum sibiricum 9 Lille Saltsö, Kangerlussuaq, Greenland 140704 (Åke Svensson) - Photo: (© 2014 Jan Thomas Johansson).

Myriophyllum sibiricum and Elodea canadensis mouth of lake Limsjön, Leksand, Dalarne 930723 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum spicatum 1 Kvinnsgröta, Gräsgård, Öland 150606 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum spicatum 2 Kvinnsgröta, Gräsgård, Öland 150606 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum spicatum 3 Kvinnsgröta, Gräsgård, Öland 150606 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum alterniflorum 11 Cloon & Laghtanabba Bog E of Claddaghduff, Ireland 170525 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum alterniflorum 12 Cloon & Laghtanabba Bog E of Claddaghduff, Ireland 170525 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum alterniflorum 2 Bäckhalladalen, Gladsax, Skåne 950610 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum alterniflorum 3 Bäckhalladalen, Gladsax, Skåne 950610 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum alterniflorum 4 W of Mandamados, Lesvos, Greece 100514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum alterniflorum 5 W of Mandamados, Lesvos, Greece 100514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum alterniflorum 6 W of Mandamados, Lesvos, Greece 100514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum alterniflorum 7 W of Mandamados, Lesvos, Greece 100514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum sibiricum 10 E of Myrland, Neidenfjorden, Finnmark, Norway 220724 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum sibiricum 11 E of Myrland, Neidenfjorden, Finnmark, Norway 220724 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum sibiricum 12 E of Myrland, Neidenfjorden, Finnmark, Norway 220724 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum sibiricum 13 E of Myrland, Neidenfjorden, Finnmark, Norway 220724 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum sibiricum 4 mouth of lake Limsjön, Leksand, Dalarne 930723 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum spicatum 10 Psarades near Lake Mikri Prespa, N Greece 180629 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum spicatum 4 Kvinnsgröta, Gräsgård, Öland 150606 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum spicatum 5 Kvinnsgröta, Gräsgård, Öland 150606 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum spicatum 6 Kvinnsgröta, Gräsgård, Öland 150606 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum spicatum 7 Kvinnsgröta, Gräsgård, Öland 150606 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum spicatum 8 Psarades near Lake Mikri Prespa, N Greece 180629 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum spicatum 9 Psarades near Lake Mikri Prespa, N Greece 180629 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum spicatum Havgårdssjön, Börringe Sk 060809 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Myriophyllum verticillatum Sandemar, Södermanland 970815 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).