Jeanne -- I thought I'd jump in here with a thought that might have value for you. I also went to the expense and work of having raised beds for my Irises. I was so sure that I was doing a great thing for my Irises -- and for me -- it would be easier for me to take care of them, do the weeding, etc., if I didn't have to bend all the way to the ground. But I made a critical mistake. The soil level in the beds is below the top of the concrete blocks that surround the Irises. Problem: first of all, by having the Irises essentially below ground level -- I was blocking air flow; second, the lowered soil level was allowing rain-water to 'pool' for a period of time. So the raised beds were holding rain water -- with reduction of air flow. For the first time in my entire life, I was having Irises rot.
It took me awhile to figure out what the problem was. I resolved it by removing the top layer of concrete blocks so that the soil sat 'above' the walls. This gave immediate drainage off the sides of the soil -- and greatly improved air flow which helped the soil to dry out inbetween rains. The rot subsided -- and my Irises immediately began to look better -- healthier.
We have heavy clay soil here in western Kentucky. I did not amend the beds before planting Irises in them because Irises seem to love this soil. I've never had a single instance of rot before planting in those raised beds, so I knew that the issue had to do with the beds themselves. I don't know what kind of soil you have -- but I thought I'd share what happened to my Irises in raised beds here.
