Parrot feather

Parrot feather (Myriophyllum aquaticum) is a relative of Eurasian watermilfoil that is rooted submerged but produces emergent feathery foliage above the waterline — distinguishes it from other milfoils. All US populations are female (sterile); spread is exclusively by fragmentation. Most common pathway of new infestations is escape from water-garden plantings, where it is sometimes sold legally despite its invasive status. Federally regulated in many states.