I am in Central Indiana and about 6 years ago we planted 3 large pampas grasses in the backyard. Each year they have grown larger and more beautiful until this year. On one, only a ring of grass around the exterior has come back. On the two others only parts of them came back. The grass that did come back is about 3-4 feet high at this time. The rest where we cut them back is still brown and not growing. We did have a long hard winter this past year but could that have done some damage? Do you think they will come back better next year? Thanks for any help you can offer.