Are you able to post a picture? Is it growing attached to a log? Do you simply want to trim the leaves to reduce the foliage or do you need to thin the plant down? If just the leaves, take sharp scissors and cut the leaf just above the rhizome. Avoid cutting into the rhizome unless you want to divide. I prune (thin) mine out by gently pulling and dividing the rhizome. Don't tear but gently pull and some of the plant will separate. To heavily divide, I use hand pruning sheers. The trick is to thin the plant incrementally over a couple of months.