Neal, I do 'heap' some of my roses with compost to help protect them over winter but usually only put the proper mulch layer on in spring after I have done my dormant spraying. Lime Sulphur is supposed to kill the spores on the surface of the soil. I say supposed to because I did spray last spring but it didn't really help much this year but then I didn't mulch ....
BTW, I have never mulched my iris - wondering if I should?
