Spring is the best time for dividing ferns, as far as I know, and it's probably still spring where you are (it's getting to be summer here). I lost a holly fern (a Cyrtomium, but the problem may be common to other ferns called holly fern) that was planted under a cypress tree. I think that either the constant "snow" of bits from the tree buried the fern's crown and rotted it, or the tree roots just got to sucking too much moisture out of the ground. In any event, pulling it up and replanting it is likely to be a good thing. Look for pests like cutworms and weevils at the same time, as ferns do get eaten too.

Thanks.