Micky's recent post asking about Roundup inspired this.
Years ago, we planted some Boston ferns around an oak tree. Their purpose was to fill in densely and prevent 1000s of baby oaks from popping up from the roots. The ferns did that admirably; however, they tend to extend their domain into areas where we don't want them. I always controlled that with Roundup.
They are at it again so eight or so weeks ago they were sprayed. No result. Two weeks later they were sprayed again. No result. Two weeks later they were sprayed yet again but with a double strength mix. No result.
I know the Roundup is good, other plants in other areas were sprayed, dead as door nails now. Any idea how/why it isn't affecting the ferns?