Nick Maclaren wrote:

Does anyone know how hardy this is? Bean says not (and that is my most
reliable source), but several other sources say that it is fairly hardy.

Nick, I grew this on several occasions in several sites 'oop't noorth
in't Midlands' where it withstood frequent exposures down to minus 8
or 10C. In each case, it was planted against south or west facing
house walls and never suffered at all. Bean is too conservative about
its cold tolerance - given the inevitable wind shelter that a wall
provides, Itea illicifolia appears remarkably tough. total freezing
of the roots will cause problems, but if you go for a house wall, the
chances of that happening even in a Cambridge winter are remote.

Dave Poole
Torquay, Coastal South Devon UK
Winter min -2°C. Summer max 34°C.
Growing season: March - November