There is a gardener in the peony forum on GardenWeb (now Houzz) that is in CA, think he's a zone 9, though. He primarily grows Itohs and tree peonies. There's also an article by Don Hollingsworth in the APS archives about forcing dormancy in peonies grown in warmer climates, he claims people have had luck with cutting them back severely during the coolest time of the year just like we do when they die back naturally in the cooler areas.
