Water milfoil : Any plant of the genus Myriophyllum, aquatic herbs with whorled leaves, the submersed ones pinnately parted into capillary divisions.

Example:


Taxonomy
Eurasian water milfoil, milfoil, lakes, stems, submersed, native plants, Wisconsin, plants, flowers, colonies, Eurasian milfoil, aquatic plant, Eurasian, water surface, Invasive Species, sediments, plant fragments, WDNR.

Defination from the web:
water milfoil is a submersed aquatic plant native to Europe, Asia, and northern Africa. It is the only non-native milfoil in Wisconsin. ... LIFE HISTORY AND EFFECTS OF INVASION: Unlike many other plants, Eurasian water milfoil does not rely on seed for reproduction. ...