Rick is right; grass is a whole 'nother story! I do seem to recall reading something about being able to use grass-specific weed killers around daylilies, you just have to be careful not to use it when the scapes are forming. And it will make the plants look strange for a while. But I'm not sure where I read that, so don't trust me on this! Does anyone else have any experience with using grass killers (NOT Roundup!) around daylilies?
