Jane et al, The only things I know of that survive glyphosate during active growth are RoundUp ready plants and some common farm weeds that have developed a separate mechanism over the years, whereby they pump the glyphosate to the leaf tips. I can virtually guarantee you that no arums fall into either category. BUT as I mentioned, it must be applied while the plant is sending nutrients to the root or tuber, later in the year, and it must be applied while the plants are unstressed and growing, below 85 F and above 65 F is preferable. Applying it to a stressed plant or one leafing out is useless and is literally against the law. You need to visit an ag chemical store and request a surfactant-free version (Honcho or Rodeo, or some such thing) for use in woodlands, wetlands, waterways, and on Christmas trees. I buy it in 2.5 gallon jugs at 41% and it's probably going for about $18/gallon now. You need to mix it up a bit stronger than recommended for spot spraying (about 10 parts water to one of concentrate by volume) , add some dish detergent and some ammonium sulfate adjuvant if available (I can send you some). Tim If there's that much arum in a wetland, it does need to come out. It will have to be dug -- the tubers can survive herbicide application.