What do you mean by "giant salvia", something 10 feet tall or something just big like Salvia leucantha? Because I live in a place that expects frosts or hard freezes in October I always grow one or two of the latter in large pots and in the fall keep those pots by the garage so they can be dragged inside on bad nights. Leucantha doesn't mind a potted life and can easily grow four feet across and three or four feet high. If I were to plant that one in the ground I'd just cut it back, plant it, and jump out of the way. Planting a leucantha in the late fall here would almost certainly kill it since it is rather tender, but you would almost certainly get a 2nd bloom. So what kind of sage are you talking about?

starts with an "s" salvia s.... i don't remember at the moment... would have to consult notes... lol