Kauri - Agathis australis

commonly known as the kauri, is a coniferous tree found north of 38°S in the northern districts of New Zealand's North Island. It is the largest - by size or volume - not height - in New Zealand, standing up to 50 m tall in the emergent layer above the forest's main canopy.

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 epiphytes from climbing. By maturity, the top branches form an imposing crown that stands out over all other native trees, dominating the heights of the forest.

The flaking bark of the kauri tree defends it from parasitic plants, and accumulates around the base of the trunk. On large trees it may pile up to a height of 2 m or more.

Although its root system is very shallow, it also has several downwardly directed peg roots which anchor it firmly in the soil. Such a solid foundation is necessary for a tree the size of a kauri to prevent it blowing over in storms and cyclones.


Kauri leaves are 3 to 7 cm long and 1 cm broad, tough and leathery in texture, with no midrib; they are arranged in opposite pairs or whorls of three on the stem.

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.

Kauri forests are among the most ancient in the world. The kauri type trees evolved during the Jurassic period (190 and 135 million years ago) and though it therefore an old type of tree it has an unusual substrate/soil interaction and regenerates in such a way that it kept competing successfully with the 'newer', faster growing angiosperms. It feeds in the organic litter near the surface of the soil through fine root hairs. This layer of the soil is composed of organic matter derived from falling leaves and branches as well as dead trees, and is constantly undergoing decomposition.

As it decays the kauri leaves acidic compounds and as they 'leach' they decayed compounds pass through the soil layers- with the help of rain - releasing nutrients trapped in the soil - typically nitrogen & phosphorus - (a process is known as podsolization, which changes the soil composition making it difficult for undergrowth or competitors to take root. The soil also changes colour - to a dull grey - an area known as a cup podsol.

Leaf litter and other decaying parts of a kauri decompose much more slowly than those of most other species. Besides its acidity, the plant also bears substances such as waxes and phenols that are harmful to microorganisms. This results in a large buildup of litter around the base of a mature tree in which its own roots feed. These feeding roots also house a symbiotic fungi known as mycorrhiza which increase the plant's efficiency in taking up nutrients. In this mutualistic relationship, the fungus derives its own nutrition from the roots. In its interactions with the soil, kauri is thus able to starve its competitors of much needed nutrients and compete with much younger lineages.

Forests containing kauri are generally known as kauri forests, though kauri needn't be the most abundant tree type to gain this description. In fact the kauri has a habit of forming small clumps or patches scattered through mixed forests


Heavy logging which began around 1820, continued for a century, and has considerably decreased the number of kauri trees. It's been estimated that before 1840, the kauri forests of northern New Zealand occupied at least 12,000 square kilometres. By the 1950s this area had decreased to about 1,400 square kilometres in 47 forests depleted of their best kauri. By 1900, less than 10 per cent of the original kauri survived. It is estimated that today, there is 4 per cent of uncut forest left in small pockets.It is calculated that around a little under half of the timber was accidentally or deliberately burnt. A little more than half of the remainder had been exported to Australia, Britain, and other countries, while the small balance was used locally to build houses and ships - superb colour and toughness but especially good for masts (few branches) and very resistant to water ... (the gum was used in varnish too...)

Giant kauri are found in North Island forests but most famous is "Te Matua Ngahere" and "Tāne Mahuta". According to Maori mythology Tāne is the son of Ranginui the sky father and Papatuanuku the earth mother. Tāne was the child that tore his parent’s parental embrace and once done set about clothing his mother in the forest we have today. All living creatures of the forest are regarded as Tāne’s children.