I have lots of clay in my soil so most of my beds are raised beds. I remove the sod, then cover the bottom with newspaper (weedblock), then add a topsoil/compost mix. Topsoil here still has a lot of that clay so without compost the ground turns hard as rock. To really keep the soil well drained I have found I need 50/50 compost to soil. Then when the iris come in I plant them with bone meal at the roots.
My Japanese & Louisiana iris are down by the creek where there is a much better organic mix in the soil. I add peat and manure to that soil, mix it really well, then let those beds sit a couple of weeks before I plant the JA or LA iris. So these beds have to be planned ahead. After planting, these beds also get a good layer of mulch to help keep the roots wet, and frequent watering.
