Huh. This is the intersectional peony that emerged from the graft on my Itoh this year. I do like it, actually, and don’t have another like it.
That means that instead of just cutting it off (which is what gardening sites mostly seem to recommend, since intersectional peonies are much less expensive than Itohs), I’ll wait ’til fall and then try to dig them and divide them, hoping they both survive the procedure. Plant surgery — exciting!