the giant of New Zealand ferns

Size
Frond: 200–500 cm
Lifespan
50–100 years
Diet
Grows in deep, damp gullies and shaded forest floors with rich, organic soils. Requires constant high humidity, deep shade, and protection from drying winds. Prefers undisturbed forest with stable conditions and cannot tolerate drought or forest clearance events.
Habitat
The king fern haunts the deep, damp gullies and shaded forest floors of northern New Zealand. It is a fern of the old places, the wet places, the places where the forest has been undisturbed for centuries. It sits on the ground, spreads its massive fronds, and waits.
Range
Found in deep, damp gullies of the upper North Island from Northland to the Bay of Plenty, and spottily down the west coast. Most common in Northland, Auckland, Coromandel, Waikato, and Bay of Plenty. Now uncommon outside of protected areas.
Endemism
Native
Main Threats
Habitat loss is the primary threat. Its range has contracted significantly since human arrival due to forest clearance, drought, and pest browsing. Also threatened by browsing by pigs and possums which eat the tender fronds, and by competition from invasive weed species.
Population
The king fern is classified as At Risk – Declining. Its range has contracted significantly since human arrival, and it is now uncommon outside of protected areas. It is sensitive to drought, browsing by pigs and possums, and the removal of the forest canopy cover.
Conservation Status
At Risk - Declining
You have seen ferns. You think you know ferns. Then you walk around a corner in a damp gully. There it is. A fern the size of a small car. Fronds reach five metres in length. They arch up and out like green cathedral arches. The trunk is not a trunk. It is a massive, woody, knobbly base. It looks like something from the age of amphibians. The king fern. The para. And it is not messing around. The scale is disorienting. Size makes it special. The king fern is the largest fern in New Zealand. It is not the tallest. That is the mamaku. It is the most massive. Its fronds are not divided into tiny leaflets like a tree fern. They are broad and fleshy. Almost succulent. They are divided into large, rounded segments. They look like they belong in a dinosaur's stomach. The whole plant is soft. Almost squishy. You could lie down on a bed of king fern fronds. You would sink in like a mattress. The texture is distinct. It is a primitive fern. The Marattiaceae family is ancient. They were around when the dinosaurs were still figuring things out. The king fern has not changed much in 200 million years. It is a living fossil. A relic of a time when New Zealand was part of Gondwana. The world was warm and wet then. The conditions suited this lineage. It persists as a testament to that era. It dominates the gully. A mature king fern can have ten or twelve fronds. Each is five metres long. They form a canopy that blocks the light from everything below. Nothing grows under a king fern. It is the king of its patch of forest. Reproduction occurs by spores, like all ferns. The spores are produced on specialised fertile fronds. These look different from the sterile ones. The sporangia are clustered in two rows along the edges of the leaflets. When ripe, they split open. They release the spores into the damp air. It grows slowly. A large king fern may be fifty, one hundred, or two hundred years old. It is not a pioneer. It does not like disturbance. It needs deep shade. It needs constant moisture. It needs a thick layer of leaf litter to sink its fleshy roots into. The requirements are strict. The tolerance for change is low. Habitat loss and browsing are causing its decline. The king fern needs undisturbed lowland forest. This is the kind that has been cleared for farms, for pine plantations, for suburbs. When the forest goes, the king fern goes. Pigs and possums also eat the fleshy fronds. They dig up the roots. A single pig can destroy a king fern in an afternoon. It is also sensitive to drought. As the climate warms and summers get drier, the king fern struggles. Its fleshy fronds lose water quickly. Without constant moisture, it wilts and dies. The vulnerability is acute. The king fern is not extinct. You can still see it in places like the Waitākere Ranges, the Coromandel, and the forests of Northland. You can walk up to it. Stand under its massive fronds. Feel like you have stepped back in time. But it is not doing well. It is the fading aristocrat. Once widespread. Now confined to the last few estates. It watches the world change around it. It does not adapt. It does not move. It just sits there, spreading its fronds, waiting for the forest to return to the way it was. And the forest is not returning. No one told it otherwise.