I disagree with that, and I have proof to back me up. Look all over the OCPS forums on outdoor bog gardening, countless people keep vfts, sarrs (EVEN S> psittacina and S. purp venosa!) outdoors YEAR ROUND.
A simple layer of mulch can solve huge issues like that. And consider that winters up here in Ontario and Quebec are long and harsh, lasting around 6 months, that just says how hardy plants are.
Do a bit of research, Scotty - while in some parts are indeed harsh, it IS possible to leave them outdoors, therefore we don't HAVE to use the ''fridge method''.