Mine are outside all year long and don't come to any great harm, neither in pots nor in the ground (except when blackbirds are looking for grubs and chuck clumps out over the grass!)

They do have a habit of mysteriously vanishing in my sinks, whether it's winter weather, or just not liking competition from nearbye plants I do not know. Perhaps hold off for a while and then buy the plant you want.

Depends where it was in the nursery g/c but living where you are I'd plant out.

Thanks everyone... i bought it in the end and planted it.