Groundcover destruction by helpful workers: how to stop it?

My mother-in-law's lawn and yard work is done by an Italian contractor whose workers don't speak much English. This situation probably cannot be changed. Part of their routine in the front yard is to hoe (or rototill? I'm never there when they do it) the soil under the shrubs until it's broken up a few inches deep. They don't seem to recognize the Phlox stolonifera and P. divaricata that I've planted as non-weeds, despite my careful positioning of markers and the wire hoop fencing I put up, and they keep chopping them to pieces! Earlier this spring they pulled off the spruce boughs I had covering the bed, and I'm afraid their next visit (possibly tomorrow) will decimate my surviving phlox.

Does anyone know a way to stop them? Does anyone know the Italian for "please don't hoe my groudcovers to pieces"? Has anyone had this problem at all (garden workers treating perennial beds as if they were weedy vegetable plots)?

Thanks,
Dawn