I might put it off until early October then. I've my fall roses coming this month so that's going to take up some time.
My peony is my usual planting mix. Native soil, gypsum, bonemeal, bagged topsoil, lots of compost. It's been working great for my roses. Hopefully the peonies like it too. I'm planning to add perlite to the mix going forth since I have heavy red clay.
I do 18 to 24 inch holes for my roses (depth & width). Can the peonies do with less if I'm just planting roots? I know they need to be about 2 inches or so below ground.