Kauri (Agathis australis) is a massive tree. Some specimens living today are over 50 metres tall and have trunks up to 4.4 metres in diameter, but larger trees, now cut down or burnt, were recorded in the 19th century. They can live for centuries – the oldest are estimated to be 2,000 years of age.
Kauri grows naturally only in the northern North Island, its southern limit being around latitude 38° south. In prehistoric times it grew as far south as Invercargill.
Until 2000, no natural regeneration of kauri had been seen south of its current limit (between Kāwhia and Te Puke). But in 2001 and 2002, seedlings sprouted next to planted, semi-mature trees in New Plymouth and Wellington. These locations are respectively 120 and 365 kilometres south of kauri’s natural range.
Kauri has flat, hard leaves, 2–5 centimetres long and 1 centimetre wide, that are often bronze-coloured in young plants. As the saplings grow they take on a conical form known as a ricker, and after 100 years or so the trees shed their lower branches and develop a wide crown and column-shaped trunk.
Seed and pollen cones are produced on the same tree. The female cone is the size and shape of a tennis ball and takes three years to ripen. When mature it disintegrates, releasing winged seeds that are carried off by the wind. Seedlings grow fast in sheltered, well-lit situations such as track edges or among tea-tree scrub.
Kauri produces a sticky white resin from cracks in its bark. This was chewed by northern Māori, who also burnt it, using the soot for tattooing. Large quantities of fossil kauri gum were dug out of Northland swamps between 1850 and 1930, for use in making varnishes and linoleum.
The timber is honey-coloured, quite soft, and even-grained. Northern Māori used the trunks for war canoes. Europeans felled hectares of kauri, at first for masts and spars for navy ships, then as a multi-purpose timber. Much of it was used for building houses, and it was also popular for boats. Supplies decreased from the 1930s, and kauri was subsequently used only as a specialty timber for furniture, veneers and boat building. Today only recycled wood is used.
The cypress family
New Zealand has two species of the fragrant cedar Libocedrus – known as kawaka and kaikawaka. Both grow into attractive cone-shaped trees with reddish-brown bark that peels away from the trunk and hangs in long, thin strips. Their leaves are reduced to pairs of tiny, overlapping scales.
Male and female cones are produced on the same tree. When ripe, the tiny, woody female cones split open and release two winged seeds. Libocedrus has been in New Zealand for at least 60 million years.
Kawaka or lowland cedar (Libocedrus plumosa) is a tree of lowland forests in the northern half of the North Island and the north-west tip of the South Island. It grows 25 metres high, with a trunk just over 1 metre in diameter. Its very flattened branchlets differentiate it from kaikawaka. The dark red wood splits cleanly, and was often used for house shingles and cabinet work.
Kaikawaka, pāhautea or mountain cedar (Libocedrus bidwillii) grows in upland and subalpine forests throughout the mainland, and seldom exceeds 20 metres in height. It favours humidity and poorly drained soils, and descends to low elevations on the West Coast where there is high rainfall.
It is long-lived, at least to 700 years. Some kaikawaka on Mt Taranaki (Mt Egmont) survived partial burial by volcanic ash during an eruption in 1655.
In the past, kaikawaka timber was sometimes used for weatherboards, boat planking and railway sleepers.