Mamaku, katata, korau, or pitau.

These are all apparently Maori names for Cyathea medullaris, the black tree fern, which is native to New Zealand and other Pacific islands.

I don't think it would grow outside here - I'm told that it won't tolerate frost. Maybe you know better! Just in case, we grow ours in a pot and take it into the glasshouse over winter, though with minimum heat.

It's a striking species, with almost black stipes and rachis. In fern terms, these are the frond stalk up to the foliage, then the midrib. 

A strong, elegant fern and easy to grow.