I have a natural stream that runs a few feet from my patio. I was given some roots that where suppose to be flag iris. Turned out to be cat tails, now I can not get rid of them. Like the cat they are named for they seem to have 9 lives. Have tried digging them out, but impossible to get 100% of roots so they grow back. Is there a reptile, amphibian fish safe vegetation killer ? Would like to spray cat tails wait till they die then dig out? If not how do you get rid of cat tails.