Plant your Japanese irises in a sunny spot with plenty of humus-rich soil. These irises are heavy feeders and require lots of organic matter for nutrients. They also need six hours of full sun.
Water is their most important requirement.
Thus they prosper near water or where the planting area is only slightly above the water table. The soil should also have a good nitrogen content. Prepare the bed with compost and manure, but avoid granular fertilizers until the plants are established. Japanese iris rhizomes must not be allowed to dry out before planting. Soak them in water for up to 48 hours before planting.