Living in cairns tropical North Queensland probably doesn't help but have a Familiar problem with nut grass by the sound of things, have searched a few forums now and all seem to refer to nut grass in lawns, but our problem only seems to be in our newly planted flower beds, the worst of all being planted with crotons, I carefully laid weed mat to all beds but obviously no match for this weed, I was going to try Sempra from Bunnings last year when I first discovered the pest but my neighbour beat me to it and has used it several times in his garden but with very little effect, I on the other hand tried tackling it the hard way by trying to pull the whole root through the weed mat (in hind sight probably made the situation worse) I now need to top my beds up with garden mix, about 150mm because of settlement but now reluctant because it sounds like I'll be giving this pest a better chance of rooting, I'm really at a loss what to do for the best, don't want to lose the crotons although some are doing better than others, and if I do try the Sempra will it harm the crotons, I'm open to suggestion