This is my favorite little park. I go here once a week and feed the turtles. This plant appeared suddenly about 3 weeks to a month ago and it's ruining the pond. I have a somewhat closeup, a picture from last week showing the way it's smothering the pond and a picture from 10 or so years ago showing the open water like it has been until a month ago. Note: 1) The "closeup" is really a tight crop of a picture similar to the wide one. 2) The green stuff on the near right side of the yesteryear picture is some kind of pond scum, it comes and goes but I've never seen it cover more than in the picture.
It has probably escaped from someones pond. We have similar problems in UK with escaped plants. It can be a huge problem. eg 1. Lysichiton americanus. Lysichiton americanus - Google Search 2. Hydrocotyle ranunculoides Hydrocotyle ranunculoides - Google Search 3. Lagarosiphon major lagarosiphon major - Google Search
