Is it good to cut them back before frost?
Certified GKH Gardening Expert
It is good to cut the stalks, and the dead growth. It is not necessary to cut the leaves. It will not hurt them, but you should leave them as they will need these to keep roots growing. Here is more information that will help: http://www.clemson.edu/extension/hgic/plants/landscape/flowers/hgic1167.html