Agathis australis Seeds | Kauri

Kauri (Agathis australis) seedling with stiff bronze-tipped leaves and a stout resinous trunk — Kauri (*Agathis australis*): Araucariaceae, the giant of Northland’s forests, now threatened by kauri dieback.

LATIN NAME: Agathis australis

COMMON NAME: Kauri

Plant Profile

Kauri is the largest tree in New Zealand and one of the largest conifers anywhere: fifty metres in height, a trunk four metres through, and a life that runs past a thousand years. The juvenile form is a narrow, stiff-leaved cone; the adult tree opens into a broad crown held above the forest on a clean, grey column.

It grows in the warm north of the North Island, on leached clay soils where rainfall is high and frost is rare. Kauri once formed extensive forests, and their remains still shape the ground: the trees drop great quantities of acidic litter, which makes the soil beneath them too poor for most competitors, so a kauri grove tends to stay a kauri grove.

Science & Biotechnology

Agathis sits in Araucariaceae, a family with a fossil record going back to the Jurassic, and its living species are scattered from New Zealand to Malesia. Kauri resin, exuded from wounds and fossilised in the ground as gum, has been studied both as a window on past climates and as a material in its own right.

The urgent research is pathological. Kauri dieback, caused by the oomycete Phytophthora agathidicida, kills trees of all ages through the roots and has spread on tracked soil. Detection dogs, soil sampling and strict hygiene at track entrances are now standard, and the disease is the reason young kauri should never be planted near infected stands.

Uses & Benefits

Historically the timber was one of the great construction woods of the South Pacific, straight-grained, durable and enormous; gum was dug and bled for varnish and linoleum. Both industries are gone, and the remaining forests are protected. Gum still washes up on northern beaches after storms, and it is collected for carving rather than for industry.

Today the tree is grown as a specimen in parks and large gardens, and as a long-term investment in the landscape. Its root system is shallow and wide, so it resists wind better than its height suggests, but it also resents compaction and drainage works anywhere within the root zone.

Growing from Seed

Sow fresh seed, since viability falls quickly. Press it into a gritty, free-draining mix, cover to its own depth, and hold at twenty to twenty-five degrees in bright light. Germination runs six weeks to three months, and the first shoot is a stout, upright cone that looks nothing like a tree.

Give the seedling a deep pot and a free root run, and do not overpot: kauri roots are coarse and slow. Grow it in bright light with protection from hard frost for the first three winters, then plant out into acid soil with plenty of surface litter. It resents disturbance, so choose the final site before the tree is a metre tall.

Our Take

A tree for the long view, and one with a biosecurity responsibility attached. Buy from clean stock, keep soil off your boots, and plant it where it can stand for centuries.

Tree Seeds