I wouldn,t put any manure in it. I did that last year even though the planting booklet that came with the iris Schreiner sent said not to use manure because it can cause rot problems. Of course I had rot problems this spring and had to bring them all up and replant with regular garden soil. The book says iris will thrive in most well drained garden soils. It says gypsum or sand or humus are a good way to improve most clay soils. I would think if you just tilled in a few bags of garden blend or sprink in a low nitrogen time release fertalizer like a 6-10-10, bone meal or superphosphate. Iris like slightly acid soil thats low in nitrogen. Personally I am going to check out coffee grounds and peatmoss when my beds are ready to be ammended next time. No more manure. (which sucks because I have horses)

Just a thought.........irises really like alfalfa. I buy it in the pellet form in either rabbit or horse feed. I just dig it in when I plant or around the established roots and it makes the soil more humusy. Probably wouldn't hurt to mulch with alfalfa hay either.

Ginny

No manure then. I have some superphosphate. I may try half the area in superphosphate & half in rabbit feed & see which do better
Thanks!