Bearded irises (Iris germanica) are some of the easiest and most beautiful perennials to include in your landscape. The name of this genus comes from Iris, the Greek goddess of the rainbow, because the flowers range in a wide variety of colors.
Irises are easy to grow as long as they are properly planted and maintained. They should be planted in late summer to early fall in well-drained soil with at least six hours of sunlight. Good air circulation aids in preventing disease; therefore, space the plants around 16 to 18 inches apart. A low nitrogen fertilizer, such as 5-10-10, should be applied in early spring when the irises are starting to grow and again at the very end of the season. A high nitrogen fertilizer may cause the plants to grow too rapidly and lead to soft rot. Also remember that irises are extremely drought tolerant and care should be taken not to overwater them. Be sure to remove the flowering stalk after blooming to prevent energy stealing seed from forming.
Divide clumps of bearded iris every three to five years. Late summer is the best time to divide, making sure that you plant the younger rhizomes that are produced off the older, center rhizome. Many gardeners make the mistake of planting the older rhizome which will not bloom a second time. At this time, you can share your extra plants with gardening friends.
For more detailed information on growing iris, see HGIC 1167, Iris.