Each year, we plant rosemary, and sooner or later a hard frost always kills it off. So this year I've experimented with leaving a cold frame over part of the herb garden (essentially, a cold frame is an angled window pane on bottom-less box).
This mild winter wouldn't have killed off the rosemary yet in any case. It's only fallen into single digits a few times and never for very long. Still, the rosemary does look happy in its little greenhouse - as do the oregano and parsley. Only the thyme seems indifferent.
And Haru would like a greenhouse of his own.