Posted: 20/11/2015 at 17:14
If it's in a pot, it can be planted at any time unless the ground's unsuitable. Of course, I'm assuming it's the summer flowering, bigger, bearded type and not a flag or Sibirica, in which case it won't mind being waterlogged! Soggy ground won't suit the former.
If it's a small or young plant, I'd leave it till spring, when it'll be a stronger plant. Just keep it in a sheltered spot to overwinter if that's the case.