For grasses in daylilies..... Google " fusilade daylilies daylily"
Fusilade is commonly used to control grasses in daylilies. Personally, I have not had a big problem with grasses, but sometimes have a small area of nutsedge get a foothold. I have used Ortho Grass Be Gone successfully. I get the small premixed spray bottle and spot spray. I think it is the same ingredient as fusilade. I believe the grass has to be actively growing for it to work.
I don't recall seeing anything about it being used when daylilies are in scape. Chemicals sometimes make the buds deform, and bloom can be affected. For example, a very small amount of overspray from roundup will ruin the blooms.
If you ask about this in the daylily forum, I am sure people more experienced with herbicides than I am could give you suggestions.
