How to Grow Purple Iris
- 1). Prepare a spot that receives full sun and has good drainage for planting your purple irises. Be sure that you plant them no later than Labor Day.
- 2). Spade the soil to a depth of at least 10 inches. Spread 5-10-10 fertilizer over the planting location and work it into the soil. Bone meal can also be added in addition to the fertilizer.
- 3). Make a ridge in the middle of the hole and spread the rhizomes over the ridge, spreading out the roots to either side. The rhizome is the thick part of the root that feels almost like a potato peeling. The rhizome only needs to be at a depth of about 1 inch below the surface of the soil.
- 4). Plant multiple plants at least 1 1/2 feet apart from each other to allow the roots to spread out. After three years of growth, the rhizomes will probably be crowding each other. At this point, you will need to divide the plants up and cut the fresh rhizome parts away from the older parts.
- 5). Apply 4 inches of mulch around the base of the plant to help protect it in winter and to keep the soil moist and rich in nutrients. Remove the mulch in the spring for a few days after the last frost of the season to let the soil dry, then apply more mulch.
- 6). Pull any weeds growing around the plant and water regularly. Water the iris more often during dry spells.
- 7). Apply dimethoate insecticide during the spring just as new growth is beginning to appear.