The World's Largest Treefern



MAMAKU – Cyathea medullaris

Black ponga, black tree fern

Family – Cyatheaceae

The world’s tallest fern, growing as high as 30 metres , with great sweeping fronds that are one of the features of Kauri forest. The caudex (trunk) alone is often over 20 metres tall, and the fronds themselves are as much as 6 metres long and over 2 metres wide.

As well as in kauri forests, Mamaku is widespread throughout lowland forest areas around the country, except on the East coast of the South Island, and including Stewart Island and the Chatham Islands.

Ferns are even older than kauri, originating in Gondwanaland some 390-million-years ago, and are considered the oldest life forms in kauri forest. Mamaku fossils have been identified from the Jurassic period, 390-million-years-ago.

Reproduction is via single celled spores that are produced in small organs called sporangia on the underside of the leaves, a system that predates seed producing reproduction by hundreds of millions of years. The spores grow into small, heart shaped gametophytes in moist soil. These develop both eggs and sperm within them, which, when one of each combines develops into a new, tiny mamaku, called a sporophyte.

The young mamaku grows very fast, as much as 50cm a year, and they can live for over 100 years. They are one of the most spectacular and common of the trees in kauri forest, their huge, graceful fronds amongst the largest of any leaf in the tree realm.

Emerging Mamaku frond.