If they're planted in the ground choose a warm sunny sunny spot, they don't like heavy soil that might become waterlogged. They don't like being moved or divided either so it must be a place where they can be allowed to establish themselves. In a very cold area of the country a mulch around the base might be a good idea in winter. If they're in a container keep well watered and they like to be quite pot bound, it encourages flowering, so no need to repot until they break free! Move pots to a sheltered place/cold greenhouse in winter. I leave the seed heads on mine because they're attractive...you can remove them if you'd rather.