Depends on whether you mean entire rhizome uprooted from soil or like we say here in my zone, plant them like you imagine a 'duck on water' their little backs and neck out of the water and their little bellies and feet in the water. In other words we plant the rhizome where you can see the top of it above the soil. But when taking irises out of the soil I never place them in the sun and the sooner they can get back into the soil the better. If I find a rhizome that has some decay on it I do one of two things depending on the amount of decay. I either leave it in place and use a spoon to scoop out all the decay and then sprinkle that area with comet and leave it exposed to heal or callous if possible, or, I take it up, cut off the decay and let it set out in the shade and dry overnight to allow the wound to callous over and then replant. I never put an iris back into the same soil where it had problems nor do I compost any iris that has problems.
