myriophyllum

[GarryDrold]

chiefly monoecious and usually aquatic herbs (as the milfoils)

[ThomasSlege]

Myriophyllum is a genus of aquatic and semi-aquatic plants in the family Haloragaceae, consisting of about 69 species. These species are commonly referred to as watermilfoil. The plants are submerged, with whorled leaves that are pinnately divided. They are typically found in freshwater habitats around the world. Some species are invasive and can form dense mats, making swimming difficult and altering the ecosystem.