We avoid any chemicals and removed limited growth by pulling the plants out by hand. It was a lot of (wet) work, but it dit the best job for 2+ years. Some plants have returned, but those are good cover for the waterfowl that inevitably arrive. I wonder if removing the seed pods will limit the growth? We also were told that if you cut off the plants below the waterline, they will not proliferate, but that theory is untested. My two cents.