My beloved cyathea dealbata tree fern (10 years old) looked as though it had succumbed to the fierce cold of the previous few months. I do, however, see some tiny green fronds appearing from the center even though the other old foliage is black and dead. What is the best way to proceed. Should I cut away all the old, black fronds (they look dreadful) or would that cause further stress to the tree?