If the pots were outside in a non protected area and they are already growing I would guess you could plant them now. Seems early though around here the earliest is around late April. When does planting normally start by you, here it is Mothers Day week.
How long ago did you plant the daylilies , have they had time to spread. If you plant them to close you will end up having to move them apart in a year or so. I would think the closest would be 12 inches apart.
