Answer: Unfortunately, any herbicide that would kill the daylilies would also kill the hostas, and depending on what you used, the grass as well. You might try lifting the hostas (they are very amenable to being transplanted and can be kept in a temporary bed) and killing out the daylilies, then replanting the hostas and reseeding or sodding the grass as needed. Keep in mind too that these daylilies can be rather difficult to eradicate. I'm sorry there's no easy way to do this.
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