Calla Lilies

I always thought of Calla Lillies as indoor plants, but the first spring we lived in this house, these guys popped up behind the garage. They always look good while they are blooming, but when they die back that area looks barren. I'd like to thing of something to interplant between these that would live during the summer and fall. It needs to be heat and drought tolerant, and like a northern exposure (mostly shade). I you have any suggestions I'd love to hear them!