It is the largest (by volume) but not tallest species of tree in New Zealand, standing up to 50 m tall in the emergent layer above the forest’s main canopy. The tree has smooth bark and small narrow leaves.
The young plant grows straight upwards and has the form of a narrow cone with branches going out along the length of the trunk. However, as it gains in height, the lowest branches are shed, preventing vines from climbing. By maturity, the top branches form an imposing crown that stands out over all other native trees, dominating the forest canopy.
Kauri leaves are 3 to 7 cm long and 1 cm broad, tough and leathery in texture. The seed cones are globose, 5 to 7 cm diameter, and mature 18 to 20 months after pollination; the seed cones disintegrate at maturity to release winged seeds, which are then dispersed by the wind. A single tree produces both male and female seed cones. Fertilisation of the seeds occurs by pollination, which may be driven by the same or another tree’s pollen.
Agathis australis can attain heights of 40 to 50 metres and trunk diameters at over 5 metres.