The ancient looking trunk of the black tree fern (mamuku) is black and covered with hexagonal scars where fronds have fallen off as it grows taller.
The koru (new shoots) and inside of trunk were baked and eaten by Māori, the pith from young fronds was also used in healing. The palisades of Māori pā (hill forts) were often built from tree ferns, which grow tall and straight.