Can you actually keep it without it overrunning absolutely everything? I took out about 60% of what I had at the beginning of the season this year, when it was still small and hadn't come out of dormancy yet. Now it's taking over the pond. I did do some replanting of my iris and waterlilies, and fertilized, but this is ridiculous. It's packed in so solid I'll need a machete to hack it apart. Any tips to keep some but keep it under control?