Kauri Grass
Astelia trinervia
A bold Astelia species with prominent midrib and parallel venation visible on broad, strap leaves. Enjoys sheltered, free-draining sites with steady moisture and filtered light. Excellent as an architectural foliage accent in temperate gardens. coastal .
Plant Description
Astelia trinervia (kauri grass) is a robust, evergreen, tufted monocot forming dense clumps of broad, strap‑shaped leaves with a conspicuous median rib and two parallel lateral nerves that give the species its name. Leaves are leathery, grey‑green to olive‑green, and arch from a short, concealed stem forming an architectural fountain of foliage. As in other Astelia, plants are dioecious: separate male and female individuals produce airy panicles of small, pale flowers in late spring to summer; only female plants set glossy, fleshy berries that ripen to orange‑red and persist into autumn and winter. Mature clumps commonly reach 40-80 cm in height and similar width, slowly expanding by short rhizomes rather than running, which makes the plant well‑behaved in gardens.
Quick Facts
| Scientific Name | Astelia trinervia |
|---|---|
| Family | Asteliaceae |
| Form | Bold, clump-forming evergreen |
| Light | Bright shade to part sun; shelter from hot winds |
| Soil | Moist, free-draining, humus-rich |
| Water | Moderate; regular moisture in summer |
| Height | 20-80 cm (tufting) |
| Spread | Clump-forming to 40-60 cm |
| Water Needs | High - consistent moisture |
| Frost Tolerance | High - tolerant of severe freezes |
| Salt Tolerance | Moderate to high (coastal species) |
| Growth Rate | Slow to moderate |
| Lifespan | Long-lived perennial |
Climate Suitability
Endemic to Aotearoa New Zealand, Astelia trinervia is most frequent in the northern North Island, especially in and around kauri (Agathis australis) forest and gumland shrublands, with outlying occurrences in north‑west Nelson. It thrives in warm‑temperate, humid climates with even rainfall and mild winters, tolerating light frosts but preferring frost‑ free or only lightly frosted sites. In cultivation it performs best where summers are not excessively hot and dry, and where soils remain evenly moist yet well drained. Exposure to salt‑laden winds is tolerated in sheltered coastal pockets, but inland shelter from hot, desiccating winds preserves the foliage at its best.
| City | Climate Suitability |
|---|---|
| Whangārei | Suitable |
| Auckland | Suitable |
| Hamilton | Suitable |
| Tauranga | Suitable |
| Rotorua | Suitable |
| Gisborne | Suitable |
| New Plymouth | Suitable |
| Napier | Suitable |
| Whanganui | Suitable |
| Palmerston North | Suitable |
| Wellington | Suitable |
| Nelson | Suitable |
| Christchurch | Suitable |
| Dunedin | Suitable |
| Invercargill | Suitable |
Habitat
Natural Distribution
Naturally occurring on leached, podsolic soils associated with kauri forests, gumlands and mānuka-kānuka shrublands, kauri grass occupies open to semi‑shaded ground on ridges and gentle slopes. It favours free‑draining, acidic substrates derived from ancient sandstones and clays where organic matter accumulates yet drainage remains brisk. In these nutrient‑ poor settings, Astelia trinervia forms part of distinctive plant assemblages adapted to low fertility and periodic drought, often alongside wire rushes, Dracophyllum, sedges and scattered shrubs.
Conservation Status
Current Threats and Protection
Classified as Not Threatened within New Zealand. Local populations can be impacted where kauri ecosystems are degraded by land clearance, track formation, or pathogen spread, and by competition from invasive weeds on gumlands. Protecting intact habitat mosaics, preventing soil movement in kauri zones, and controlling invasive species help sustain recruitment of Astelia and its associates.
Growing Requirements
Soil
Humus-rich but free-draining; avoid boggy sites.
Light
Bright shade or morning sun; protect from leaf scorch.
Water
Moderate, consistent moisture; mulch to conserve water.
Planting Guide
Best Planting Practices
Plant in the cool, moist months. Dig a broad hole and improve backfill with composted bark and mineral grit to enhance porosity; set the crown fractionally proud of the surrounding soil to avoid water sitting around the base. Water to settle, then mulch with leaf litter or fine bark, keeping material clear of the crown. Space clumps 40-60 cm apart for a knitted, weed‑suppressing ground layer.
Ecological Role
Environmental Benefits
Astelia trinervia contributes structure and seasonal resources in northern forest and gumland mosaics. The flowers provide nectar and pollen for invertebrates, and the showy berries on female plants are eaten by birds which disperse seed to new sites. Dense clumps help armour fragile soils against erosion and create cool, moist microsites that benefit seedling establishment of other natives.
Uses
Traditional and Modern Applications
An outstanding foliage plant for shaded borders, courtyards and naturalistic restoration. Its slow, clump‑forming habit suits containers, narrow beds and under‑storey drifts, and it reads crisply against fine textures such as ferns and sedges. In restoration, eco‑sourced plants help re‑create kauri‑associated understories on appropriate soils.
Landscaping Uses
Garden Design Applications
Excellent for rock gardens, alpine collections, and naturalistic plantings. Best used in open, well-drained positions where its distinctive form can be appreciated. Combines well with other native alpine plants and provides year-round structure. Consider placement carefully due to sharp foliage - avoid high-traffic areas. Creates dramatic focal points in contemporary and native-themed garden designs.
Seasonal Care
Year-Round Maintenance
Spring: refresh leaf‑litter mulch, remove winter‑tattered leaves and check drainage. Summer: water deeply during extended dry spells and protect from hot, drying winds. Autumn: divide congested clumps if needed and tidy spent flower stems. Winter: avoid waterlogging around crowns and site away from frost pockets in colder districts.
Pruning
Pruning Techniques
Minimal pruning is needed. Cut entire damaged leaves cleanly at their base rather than trimming tips, and remove finished flower panicles on female plants after fruiting.
How to Grow Kauri Grass
From Seed
Propagating Astelia trinervia from seed involves collecting ripe, berry-like fruits (which turn reddish). Clean the pulp from around the seeds thoroughly, then allow them to dry slightly. Many Astelia species benefit from cold stratification to break dormancy; a period of 1-3 months in a refrigerator within a moist medium is often recommended. Sow the seeds on the surface of a well-draining seed-raising mix (e.g., peat, perlite, sand), as they often require light for germination. Keep the medium consistently moist but not waterlogged, and provide warmth (18-22°C or 65-72°F) and high humidity. Germination can be slow and erratic, potentially taking several weeks to many months. Once seedlings are large enough to handle, transplant them into individual pots with a suitable growing medium. Growth from seed can be quite slow, with plants taking several years to reach a substantial size.
From Division
Division is generally a more reliable and faster method for propagating Astelia trinervia, and it ensures that the new plants are genetically identical to the parent. The best time for division is in spring or early summer when the plant is actively growing. Carefully dig up the mature plant or remove it from its pot. Gently separate the clumps of rhizomes, making sure each division has a good root system and at least one or more healthy growing points (fans of leaves). A sharp, clean knife may be needed for dense rhizomes. Replant the divisions immediately into appropriate containers or directly into the garden at the same depth as before. Water thoroughly after division and keep the new plants in a sheltered, shady location until they establish new growth. This method provides a quicker route to mature plants than seed propagation.
General Cultivation
Astelia trinervia, also known as forest astelia or perching lily, is naturally found in damp, shady forests, often growing epiphytically or lithophytically, but also terrestrially. In cultivation, it thrives in partial to deep shade; direct, harsh sun can scorch its leaves. For terrestrial planting, it requires well-draining, humus-rich, acidic soil. Heavy, waterlogged soils should be avoided to prevent root rot. If grown epiphytically or lithophytically, use bark mixes or sphagnum moss. It needs consistently moist conditions, especially during warmer months, but must not be waterlogged. It prefers cool to moderate temperatures and high humidity, so protect it from frost, particularly when young. Light feeding with a balanced liquid fertilizer during the growing season can benefit potted specimens. Ensure good air circulation to prevent fungal issues in humid conditions.
Pests and Diseases
Common Problems and Solutions
Well grown plants are generally pest‑free. Prolonged winter wet can cause crown and root rots-improve drainage and keep the crown slightly elevated above surrounding soil. In still corners scale and sooty mould may develop; increase airflow and wipe foliage if required. Snails may graze young divisions; hand‑pick or use pet‑safe barriers.
Cultural Significance
Traditional Uses and Values
Kauri grass is a characteristic component of northern forest and gumland vegetation. By supporting nectar‑ and fruit‑feeding fauna and helping to bind vulnerable substrates, it contributes to ecosystem resilience. Using eco‑sourced plants in restoration acknowledges local whakapapa and helps sustain authentic community composition.
Bonus Tip
Expert Growing Advice
Commonly known as "Kauri Grass" because it is a constant companion in Kauri forests of the North Island. It indicates the specialized, acidic soil conditions that Kauri trees prefer.
