I remember the one in that picture from when I lived in a warmer climate, unfortunately I don't have one here because it wouldn't be hardy but I thought yours resembled it. But I can't directly compare. Did you plant it with an intact rootball? Sometimes what can happen is that the potting mix dries out and if you don't water it heavily before planting it isn't able to rehydrate even in fairly wet soil. That's what I was wondering about as a possibility. If it is a water insufficiency issue the plant would tend to look better in the mornings and then droop as the day wears on, then be recovered again by the next morning. Can you direct some water right at the base of the plant and see if that helps?
