I have read that you can mulch lilies...
Mulch is another important factor with lilies, as with many herbaceous perennials. A thin layer (5 cm/2 in.) of Premier bark mulch not only helps the soil stay cool and keeps weeds down, it also holds the mounded soil from washing away during heavy rains.
I know that you can mulch
roses. I have my
roses mulched with cedar bark chips & they are huge & beautiful & very healthy. Although I am not sure about fine ground mulch, since it will not be as porous or allow for as much air circulation.