The only info I have about hardiness is from the Stoke's Tropicals catalog. It says cold hardy in zone 9 which has a low of 20-30 degreees. I would definitely bring it inside before frost gets on it.

Frost will get the leaves, but surprisingly it grows at rather cold temps. To make sure it is dormant before you cold-store it, bring it in when it's a few degrees above freezing. Don't worry about the leaves, you will have to cut these off anyway before storing cool.

Erlend