Another thank you to van swearingen@Flickr (original | BPotD Flickr Group Pool) for sharing an image with BPotD. Do note that even though this is the correct orientation of the photograph, the image posted on Flickr has been rotated by 180 degrees. I agree with the photographer that it appears more attractive that way, but you can judge for yourself.
Parrot's feather or Brazilian water-milfoil is native to most central and southern South American countries; you can observe it, though, in many other places. It is difficult not to notice the words “invasive”, “weed” and “alien” when browsing through the search engine result summaries. The species is present in the Global Invasive Species Database (Myriophyllum aquaticum), where it lists the alien range of the species as “Australia, Europe, Indonesia, Mediterranean, New Zealand, South Africa, United Kingdom and United States”.
The Washington State Department of Ecology provides an excellent fact sheet on Myriophyllum aquaticum. In part, it explains the spread of the species: its use in outdoor and indoor aquaria as well as aquatic gardens. Escapes from cultivation occur, as well as misguided intentional plantings. Attractive as it is, it can form a thick layer at the water surface, blocking light from penetrating deeper into the water body. Subsequent population declines in microscopic algae lead to an eventual withering of invertebrate and fish populations.