It is best to plant irises before the end of September or October in warmer areas, giving them plenty of time to become established before winter. Most irises (bareroots or bulbs) can be transplanted during the late summer and early fall. If you have irises from containers, they can be put in the ground in the spring.
Most iris, especially bearded iris, will need full sun for most of the day. In extreme heat, some shade in the afternoon is advised to keep flower colors from fading. When they bloom depends on your climate; in warmer areas, they are up and at it by mid-spring, whereas farther north they may be an early-summer standout.
Most varieties love very moist to wet soil, but they may be prone to fungi and other moisture-loving pests. To prevent this you should plant your iris in an area with good air circulation to help prevent disease problems.