If a border or a closed bed is desired, then 12-16 inches is a good spacing to use. Anytime is the best time to plant daylilies, provided you get them in the ground a month or six weeks before your severe freezes. If winters are severe, plant evergreens only in the spring or summer, so that they can become well established before winter. Cut off winter damaged foliage in the spring before new growth begins. Dormant daylilies are not recommended for tropical climates like southern Florida.
Evergreen daylilies are excellent for southern climates.