Iris hollandica Plant bulbs in the fall 4" deep and 3-6" apart in well-drained average soil in a sunny to shaded location. They'll bloom better when planted in full sun. In colder regions, mulch after ground freezes. Allow foliage to ripen through summer and then gently remove. For greater impact, plant several bulbs in an area. They do best when allowed to form thick clumps over 3-5 years, after which flowering will diminish. Lift while dormant and remove and replant offsets that form along mature bulbs. Grows 24" tall and 12-18" wide. Blooms May-June. Hardy in zones 4-9.
Iris reticulata and danfordiae Plant in welldrained soil in full sun. Space the bulbs 3-4" apart and 2" deep in clumps of 4-6. Water well during their growth period. Mulch lightly over the winter for protection. Leave undisturbed after foliage dies back. Reticulata blooms February-March, and Danfordiae blooms late January-early February. Hardy in zones 4-9.