Sorry to learn about your trouble growing iris. But honestly, they are so beautiful in bloom that they are worth the trouble. The planting on the slope for drainage sounds like a good idea.

I like to plant my iris very high to prevent rot and then no mulching. Just use Preen around them to stop the weeds.

I don't know why the blooms would rot off. Have you tried using a systemic fungicide on them? Couldn't hurt.

I think your idea of planting on the slope will work too, or in a raised bed. We've had record rains the last 2 years, I don't think I actually lost any rhizomes from it. They do look rather rough right now, but they bloomed well. The worst problem was from heavy winds that blew the stalks over.I've never had the blooms rot off either, occasionally I will have a new plant bloom low in the foliage. Hope your plan works, they are beautiful.

I would be so frustrated. It has to end sometime, doesn't it?

No weeds I keep the beds weed free. I am already on a raised bed and sloped but I am putting the new bed on a really steep slope and I am going to till in alot of sand. When I put those beds in I used a garden blend topsoil so maybe its just to rich for iris. Its just so frustrating because for many years at the old house my iris bloomed year after year and were carefree. Up here I have bent over backwards to get them to thrive and they do right up to blooming time then rot sets in. I am beginning to wonder if part of it is the iris them selves. I have been spending hundreds of dollars a year on new releases and they just don,t seem as hardy. But then again when it rains almost every single day right up to and threw bloom season for several years in a row thats something I cann,t control. I just been bitten by the iris bug big time and its driving me crazy that I am having so much trouble growing them. It has to stop raining sometime doesen,t it?