I'm speaking from experience, im that guy who said you might have to get out every root. Maybe we were special or maybe it was just the right environment but I started finding it in random patches coming up all over my old back yard. We tried digging it out, burning it, someone suggested tar, but nothing ever quite got ours. I wasn't alone, but I was probably talking to other people who had it bad too. No one complains if everything is fine.
I'm in a new house now, but never again for me.