How big around is the clump Chelle? If they are in a important diplay area, I would just take some cuttings here and there and make the two look balanced. Each cutting should root easily for you. Do you have them in full sun? If not they will tend to get floppy. If in full sun they will stay very upright. I don't ever have to tie or stake mine. I love the winter interest from the wonderful spent flower heads.
