I want to get some new daylilies to replace some of the doubles (two of the same plant, not doubled blooms) I have in my garden. However, I have some seed pods setting on the plants that I am planning on replacing. I know, poor planning on my part. Anyway, I was wondering how late is too late to plant daylilies in zone 6a. Is there a suggested "x number of weeks before the projected first frost" for daylilies?