Planting iris plants is very easy to do, and can be a rewarding experience. When an iris is purchased, it will be either in bulb or rhizome form. If the iris is in bulb form, planting it is just like planting any other bulb plant. Planting iris bulbs should be done at a depth of about three inches, making sure that the bulb is facing the correct way up. This should take place in the fall, as the plant will then become dormant for the winter and then grow in the coming spring.