Safely dig up and replant an iris by doing so after its blooming period, using a spade to pry up the rootball, shaking off any soil and soaking the roots in a Clorox mixture. Once replanted, water the iris well.
After the iris blooms, during the summer or fall, water the soil around the plant until it becomes pliable, then use a gardening spade to dig out the root ball. Shake and spray off any extra soil, and divide the iris if needed. An iris needs to be divided if the plant produces fewer flowers or if the rhizomes start growing above ground. Remove all but the mother or main rhizome, often recognized by the attached bloomstalk. Break off and discard all other rhizomes except the ones that were attached directly to the mother, which you can plant.
Two weeks before replanting the mother rhizome, amend the soil with 4 inches of organic compost and a 12-12-12 ratio fertilizer, working them into the top 12 inches of soil. Place the rhizome for 20 minutes in a mixture made of 10 parts water and one part Clorox, and rinse it before placing it in a hole in the ground. Cover all but the top of the rhizome with soil, and water it well.