It's a wetland but you're going to plant switch? Smart weed thrives in wet soil, and even though you can kill the plant there are billions of seed in the bank. I kill it with descent success in clover all the time with Imox. I'm sure there are better chemicals since you aren't worried about clover, like I am. 2,4-D kills it on my place too, but I've heard of resistant weeds it won't kill. I love smartweed in a wetland, so do the ducks!