The walking iris (genus Neomarica), also called the apostle plant, sends out "baby" plants from the tips of its stems, somewhat like a spider plant. It can be grown outside in temperate zones 8-10 (lowest temperature, 20 degrees F), but is grown as a house plant in most cooler zones. Pruning is mainly a matter of harvesting the babies at an appropriate time.
Allow the plant to get pot-bound--that is, the roots filling the pot. You might think it look overcrowded, but walking irises bloom more when they don't have much room for their roots. From each bloom, which often lasts only a day, a new plant will spring.
Guide each new plant (while it's still attached to the mother plant) down into a receptacle that will become its first new home after it is cut from the mother. New plants will take root in either a small pot with potting soil or a container of water.
The stem with the baby plant will bend down with its root buds extended, ready to plant itself. When it gets near the waiting pot, but still attached to the mother plant, loosen the potting soil and plant it, or slide it into the water and transfer to a pot after the roots emerge.
Allow the plant to take root in the pot and then clip the connection with the mother plant. If it has been rooted in water, transfer it to a small pot. In either case, keep the small pot moist and let the new plant become pot-bound before transplanting it into a larger pot.
Walking iris may be grown in the garden in semi-tropical zones of the Gulf States or California. In the garden, leave room around your original walking iris for babies to plant themselves in a ring around the mother. They will quickly fill up a bed.
Alternatively, clip and transplant the baby plants when they have grown about 6 inches tall. Gently dig around the shallow roots, cut the connection with the mother plant and plant it elsewhere in the garden.
You may allow garden plants to transplant themselves into pots the same way you would a house plant. Bring the small pots indoors, or share them with other gardeners. Although Neomarica is not a true orchid, some orchid fanciers prize it for its short-lived, but brilliantly colored, fragrant flowers.