The iris is a rhizome-growing perennial plant available in the colors of blue, purple, yellow, red and pink. The plants bloom in early summer with some varieties reaching a height of 4 feet with the thick, green foliage blades remaining a garden focal point through the summer months. Some varieties will re-bloom in late summer and early fall when properly cared for. Iris plants multiply quickly and should be divided every four to five years or once the rhizomes become crowded.
Choose a planting location that has well-draining soil and full sunlight conditions. Prepare the area by working the soil with a tiller to a depth of 12 inches. Till in 2 to 4 inches of compost.
Dig a hole that is 10 inches wide and 4 inches deep. Make a ridge down the center of the planting hole. Place the iris rhizome over the ridge with the roots spread out on each side. Gently cover with soil and pack in place.
Water the rhizomes well after planting for the first growing season. Normal rainfall is adequate for watering in most areas. Supply water if the rainfall amounts are less than one inch per week during the growing and blossoming season.
Apply a layer of compost around the iris plants each spring. Fertilize the iris plants in spring with a 5-10-10 low nitrogen fertilizer once plant growth has started. Apply another dose once flowering is complete.
Cut spent flowers after blooming. Prune dead foliage to the ground level in the fall season and healthy leaves to a height of 4 to 5 inches.
Protect the iris plants in cold climates where there is no snow cover for insulation. Apply airy mulch or evergreen branches over the top of the plants. Do not use wood chips or organic mulch as this will promote root rot.
Divide iris plants every four to five years in the late summer months. Dig the rhizomes from the ground and separate them into groups of one to two leaf fan sections. Discard rhizomes that appear diseased or have few white roots present.