I found this Peony blotch

The late-season blotch phase provides the overwintering inoculum for the next year's infection, especially in older varieties. Fungicides work only to prevent infection; once the disease takes hold, there is no treatment.

===>>> what does that mean??

spray in fall to kill the spores ...

and.. does it mean.. once you see it ... its too late for this year????

i think you said you are moving it from part shade to sun ... that might help .. especially if you increased air movement .. per section 4 of the ipm strategy at the link ...

ken

Nope, opposite -- moved it from sun to part shade yesterday (moved to west side of house), but the spot is drier. If it doesn't do well there, I can move it to the vegetable garden where it's hot blazing sun all day and nothing to obstruct wind flow. I don't know if I can bear to part with her, I bought the thing as a one-stick wonder in a body bag at my very first house - what, 20+ years ago? - so I'll just keep trying...

Here she is in full glory back at the last house: