If you haven't already divided your tall bearded iris by now, it's time to get it done. I live in USDA Zone 5, and my iris need the last of the warm season to get settled in to their new homes
Dig up the clump and separate the rhizomes by slicing them apart with a sharp knife. Disinfect the knife between cuts by dipping it into a 10% bleach solution (one part bleach, 9 parts water). Keep the rhizomes that are at least three inches long, have good roots and a fan of leaves. Cut the leaves back to about eight inches. Throw away any rhizomes that are shrunken, have holes or mushy parts. Dispose of the unwanted material in landfill rather than composting it, to avoid spreading disease.
Those rhizomes you choose to keep and replant should be briefly disinfected in the bleach solution and then left to air dry for a day. When you replant the iris, be sure that the top of the rhizome is just at the surface of the soil.
My iris tend to rise up out of the soil over the winter. I think the solution is to water well and press down around the rhizome to be sure there are no air pockets when you replant. If a rhizome still looks like it's riding a little high on the ground, I might side dress it with compost before winter sets in. Be sure not to bury the rhizomes in the compost.