Agathis australis aka Kauri

Agathis australis, or kauri, is native to New Zealand’s North Island. It belongs to the Araucariaceae family and keeps its leaves year-round. This conifer has broad leaves rather than needles. It forms a huge tree with a thick, straight trunk. Kauri also holds deep cultural value for Māori. They lead efforts to protect the species and its forests.

Young trees have a pyramid shape and grow slowly. They may keep this form for more than 50 years. The RHS lists garden heights above 39 feet [12 metres]. It gives a spread beyond 26 feet [8 metres]. Oregon State reports heights of 100–160 feet [30–50 metres]. Mature trunks show little taper from base to crown. On large trees, branches may start 49 feet [15 metres] above ground. Branches spread sideways, often in whorls. They fall away at their bases after their leaves die.

Thick, blue-grey bark peels off in large plates. The tree makes large amounts of resinous gum. Its flat, tough leaves change shape as it ages. Young plants have longer, narrow leaves that stand upright. Older trees carry shorter, oblong leaves in dense groups. Leaves can grow alternately or in opposite pairs. Male and female cones usually share one tree. The male cones are narrow cylinders that hold pollen. The woody female cones are round and contain seeds.

Grow kauri in sun, though it also accepts partial shade. It needs moist soil that lets excess water drain away. The RHS lists neutral loam and a sheltered site. It rates kauri H3 for mild or coastal UK areas. Oregon State places its cold limit at USDA Zone 9. Young plants can grow in a cool greenhouse for their foliage. Use peat-free, loam-based compost, good light, and ample airflow. Plants can stand outdoors during summer. The RHS suggests containers, patios, courtyards, and city gardens. Sow seed with warmth in early spring.

The RHS reports few routine pest or disease problems. Yet kauri dieback poses a grave threat in New Zealand. The soil-borne organism Phytophthora agathidicida causes this disease. It can rot roots and the trunk base. Other signs include leaking resin, yellow leaves, and leaf loss. Infected trees may die, and no established treatment exists. Some forests have closed to visitors to limit its spread.