You know it when you see it, and you’ve tried to justify it’s “beauty” because your clients ask for it and the nurseries continue to carry it. It’s ugly because it is a piece of the destructive puzzle that is the OLD NORM of California gardening. There will be a day when designers (including landscape architects) and landscape contractors are held liable for projects like this that contribute to the degradation of the local watershed. Be a leader of the NEW NORM instead.
Become a Watershed Wise Professional. Educate your clients about this unholy trio: Cortaderia selloana (Pampas grass), Pennisetum setaceum (Fountain grass), and Nassella (Stipa) tenuissima (Mexican feather grass). Select California native non-invasive alternatives, and advocate at nurseries to discontinue selling them (including so-called “sterile” varieties).
Look to your local California Native Plant Society for more information about non-native invasive species and appropriate local native alternatives.