Answer: Daylilies need their foliage all season to help nourish the roots, but could possibly be trimmed in mid to late summer after they have bloomed. Bearded iris can be mowed off in mid summer when the foliage begins to flop over, if you are careful not to damage the rhizomes. Iris tend to fade away if left unweeded and do not make a good groundcover for this reason. They also may develop rot problems if weeds or grass overshadow the rhizomes. The typical orange daylilies (Hemerocallis fulva) are good competitors however and should do well as a ground cover, eventually crowding out most other growth. Good luck with your project!
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