Kāmahi
Pterophylla racemosa
Kāmahi (Pterophylla racemosa) is one of Aotearoa New Zealand's most common forest trees. It forms a graceful, often multi-stemmed crown and produces abundant creamy-white flower racemes that are a valuable nectar source for insects and birds. Naturally widespread from coastal to montane forests across much of New Zealand, kāmahi is resilient, adaptable, and a reliable nurse/canopy tree in restoration plantings. Learn more in our native plants guide.
Plant Description
Botanical Features
Kāmahi (Pterophylla racemosa), formerly known as Weinmannia racemosa, is an evergreen tree endemic to New Zealand. It can grow up to 25-28 meters in height, with a trunk up to 1.2 meters in diameter. The tree has dark green, leathery leaves, approximately 7.5 cm long and 4 cm wide. Its foliage is heterophyllous, meaning it has distinct seedling, juvenile, and adult leaves. Adult leaves are simple, elliptic to broad-ovate, with coarsely, bluntly serrated margins. Kāmahi produces masses of creamy, white, or pale pink flowers between October and March, which have a sweet, scented smell. These flowers form in erect, spike-like clusters (racemes) that are 60-140 mm long. The fruit is a pubescent, broadly cylindrical capsule, 4.0-5.8 - 2.7-3.1 mm, which dries to a honey-brown or dark brown color. It contains numerous small, orange-brown seeds with dense hair tufts at their apices. Kāmahi is durable, hardy, and persistent, growing well in most situations. It often starts as a dense shrub but can develop into a large tree. It is a slow-growing plant that takes time to establish roots. It can also start life as an epiphyte, growing on tree ferns.
Quick Facts
| Scientific Name | Pterophylla racemosa |
|---|---|
| Common Name | K01mahi |
| Height | 1013151125 m (occasionally taller) |
| Spread | 6110 m |
| Growth Rate | Moderate |
| Light | Full sun to partial shade |
| Water Needs | Moderate; keep evenly moist while establishing |
| Frost Tolerance | Good once established |
| Salt Tolerance | Low |
| Lifespan | Long-lived |
Climate Best Suited to
Regional climate suitability across major New Zealand cities.
Regional Suitability
| City | Climate Suitability |
|---|---|
| Whangārei | Good |
| Auckland | Ideal |
| Hamilton | Good |
| Tauranga | Ideal |
| Rotorua | Good |
| Gisborne | Good |
| New Plymouth | Good |
| Napier | Good |
| Whanganui | Good |
| Palmerston North | Good |
| Wellington | Ideal |
| Nelson | Good |
| Christchurch | Moderate |
| Dunedin | Moderate |
| Invercargill | Moderate |
Natural Habitat
Kāmahi (Pterophylla racemosa), formerly known as Weinmannia racemosa, is an evergreen tree endemic to New Zealand. Its natural habitat spans a wide range of environments, from coastal areas to subalpine regions, making it one of Aotearoa New Zealand's most common forest trees.
Key Habitats Include:
- Coastal to Subalpine Forests: It is frequently found in disturbed habitats within coastal, lowland, and montane forests. It can become a dominant tree in higher elevation montane forests, particularly in the elevated areas of the North Island and the western South Island.
- Regenerating Bush and Disturbed Areas: Kāmahi is commonly observed in regenerating bush, along clay banks, and flourishing at the edges of roads and streams. Its ability to colonize disturbed sites highlights its role as a pioneer species.
Preferred Conditions:
- Moist, Well-Drained Soils: It prefers moist, fertile soils that are free-draining but will tolerate a wide range of soil types, including weathered clays on hill country. Avoid prolonged waterlogging.
- Light: It grows from open sun to dappled forest light, making it excellent as a nurse canopy in restoration sites.
- Climate: Its distribution covers a significant portion of New Zealand, from Auckland in the North Island down to Stewart Island, adapting to diverse climatic conditions. It is hardy across much of Aotearoa, though young plants appreciate shelter from severe frost and wind.
Unique Growth Habit:
- Epiphytic Start: Interestingly, Kāmahi can begin its life as an epiphyte, growing on tree ferns, before developing its own root system and becoming a freestanding tree.
The widespread presence and adaptability of Pterophylla racemosa underscore its ecological importance as a resilient and reliable nurse/canopy tree in restoration plantings and its contribution to the biodiversity and structural complexity of New Zealand's native forests.
Plant Conservation
Conservation
Pterophylla racemosa, commonly known as kāmahi, is an evergreen tree endemic to New Zealand. It is a widespread and common tree found across the North Island, South Island, and Stewart Island/Rakiura, thriving in various climatic conditions from coastal to subalpine areas. It is often locally dominant in disturbed habitats and higher elevation montane forests. Despite its prevalence, the Department of Conservation monitors kāmahi forests, particularly due to the damage caused by introduced species like possums. Possums can harm kāmahi trees from the canopy to the ground, as the trees have not adapted to these invaders and have little protection against them. However, given the tree's commonality throughout New Zealand, possums are not considered a significant threat to the species as a whole. The conservation status of Pterophylla racemosa has been consistently classified as "Not Threatened" in New Zealand, according to assessments in 2004, 2009, 2012, and 2017. It is considered a resilient and adaptable species, making it a reliable nurse/canopy tree in restoration plantings. Propagation of Pterophylla racemosa is relatively easy from fresh seeds, and it can also be grown from semi-hardwood cuttings, though with variable success rates. The tree prefers well-drained soils and tolerates a wide range of conditions, including infertile soil, and can grow in open sun to dappled forest light. Its flowers are a valuable nectar source for insects and birds.
Growing Requirements
Soil
Prefers fertile, well-drained soils but tolerates a wide range, including weathered clays on hill country. Avoid prolonged waterlogging.
- Best in moderately fertile, free-draining substrates
- Tolerates slightly acidic to neutral pH
Light
Grows from open sun to dappled forest light; excellent as a nurse canopy in restoration sites.
Water
Keep evenly moist during establishment; once rooted in, k01mahi is relatively drought-tolerant in many regions.
Temperature
Hardy across much of Aotearoa; young plants appreciate shelter from severe frost and wind.
Planting Guide
Site and Soil
Kāmahi (Pterophylla racemosa) establishes best in moist, well-drained, mildly acidic soils from lowland to montane sites. It tolerates high rainfall, frequent cloud, and exposed hill country but performs poorly on waterlogged, compacted ground. Choose a position with full sun to partial shade and shelter young trees from severe coastal winds.
Planting Steps
- Weed an area of at least 1 m diameter; remove turf and competing grasses.
- Dig a hole twice the rootball width and the same depth; loosen the sides for easy root penetration.
- Set the tree at the original nursery depth; backfill with native topsoil blended with composted organic matter.
- Water thoroughly to settle soil; apply a 5-8 cm mulch, keeping it clear of the trunk.
- Stake in very windy sites to prevent rocking during the first 12-18 months.
- Water weekly through the first dry season; reduce as roots establish.
- In possum-prone areas, use guards or repellents to protect new foliage.
Spacing and Companions
For restoration or shelter, plant at 2-3 m spacing. Associates include Beilschmiedia tawa, Weinmannia silvicola (regionally), Metrosideros umbellata in wetter southern areas, and understory shrubs such as Coprosma, Pseudopanax, and Hebe/Veronica species.
Ecological Role
Nectar and Habitat
Kāmahi is a prolific nectar source; its racemes attract tūī, korimako/bellbird, and a wide range of insects. The dense canopy and persistent leaf litter create cool, moist microhabitats that support ferns, epiphytes, and invertebrates on trunks and branches.
Succession and Stability
Common in mid-successional forests, kāmahi acts as a nurse tree, rapidly occupying slips and hill country and facilitating later-canopy species. Fine, wind-dispersed seeds assist colonisation after disturbance; established roots help bind steep slopes and reduce erosion.
Herbivory Pressure
Foliage is highly palatable to possums; browse can suppress flowering and canopy health. Effective animal pest control markedly improves stand resilience and flowering intensity.
Uses and Significance
Garden and Restoration
K01mahi is widely used in revegetation for its reliable establishment and value as a nectar source. In gardens it provides year-round structure and spring display.
- Canopy and nurse tree for restoration projects
- Nectar source supporting insects and birds
- Attractive spring flowering for mixed native plantings
Cultural and Ecological Notes
The bark contains tannins historically used for dyeing and leather tanning; the flowers contribute to distinctive k01mahi honey in some regions.
Landscaping Ideas
Shelter and Structure
Use kāmahi as a fast-establishing shelter or backdrop in high-rainfall and hill-country gardens. Its textured trunk and seasonal flower display add vertical interest to mixed native plantings.
Riparian and Slopes
Plant on the upper banks of streams and along gullies (above flood-scour level) and on stabilised slopes to provide shade, bank binding, and wildlife corridors.
Seasonal Care Calendar
Spring
- Plant or transplant as soils warm
- Mulch to conserve moisture
Summer
- Water during extended dry spells
- Monitor for pests on soft growth
Autumn
- Top up mulch; light formative tidying
- Collect seed from mature capsules where permitted
Winter
- Plant bareroot/eco-sourced stock in suitable regions
- Stake young trees in windy sites
Pruning and Maintenance
Techniques and Timing
Generally low-maintenance. Focus on formative pruning when young to develop a single or well-spaced framework. Remove damaged or crossing stems as needed.
How to Grow Kāmahi
Kāmahi (Pterophylla racemosa) is one of Aotearoa New Zealand's most common forest trees, forming a graceful, often multi-stemmed crown. It produces abundant creamy-white flower racemes that are a valuable nectar source for insects and birds. Naturally widespread from coastal to montane forests, Kāmahi is resilient, adaptable, and a reliable nurse/canopy tree in restoration plantings. Understanding its propagation methods is key to successfully cultivating this important native tree.
From Seed
Propagating Kāmahi from seed is generally the most reliable method. Collect ripe capsules in late autumn or early winter, when they begin to dry and split. Extract the small seeds and sow them fresh for best results. A brief period of cool stratification (e.g., refrigerating seeds in moist sand for 4-6 weeks) can improve germination rates and ensure more even sprouting. Sow seeds thinly on a well-draining seed-raising mix, lightly covering them with fine medium. Keep the seed tray consistently moist and in a sheltered position with bright, indirect light. Germination can be slow and irregular, often taking several weeks to months. Once seedlings have developed a few true leaves and are stable, carefully prick them out into individual small pots, minimizing root disturbance. Grow them on in a sheltered environment with steady moisture before gradually hardening them off for planting out.
From Cuttings
Semi-hardwood cuttings of Kāmahi can be attempted, but success rates are often variable and generally lower than with seed propagation. Take 10-15 cm cuttings from healthy, non-flowering shoots in late summer or early autumn. Remove the lower leaves and dip the cut end in a rooting hormone. Insert the cuttings into a well-draining propagation mix (e.g., sand and perlite) under mist with bottom heat (around 20-25°C) to maintain high humidity and encourage rooting. Keep the cuttings in bright, filtered light. Rooting can be slow and may take several months. This method is generally more successful for experienced propagators or in specialized nursery settings with controlled environmental conditions.
Pests and Diseases
Kāmahi foliage is highly palatable to possums; browse reduces flowering and canopy health. Implement regional pest control or use temporary guards on young trees. In gardens, occasional scale and sooty mould can develop in still, humid conditions - improve airflow and wash affected foliage. Waterlogging stresses roots; maintain free drainage on slopes and avoid compacted sites.
Cultural Significance
Cultural Importance
Kāmahi in Culture
Pterophylla racemosa, commonly known as Kāmahi, holds significant cultural importance, particularly in New Zealand where it is an endemic tree. It was highly valued by Māori before European arrival and was considered almost sacred, protected by tapu (spiritual restriction). Legends suggest that Māori were careful not to cut down all the limbs of a Kāmahi tree, believing that doing so could lead to unfortunate consequences for themselves or their spouses. The bark of Kāmahi contains tannins, which were historically used for dyeing and leather tanning, producing a reddish-brown, colorfast dye. The inner bark was used as a purgative decoction and a laxative. It was also infused in boiling water to create a tonic. While pre-European medicinal uses primarily addressed digestive and skin issues, the bark's tannic acid was an astringent for dysentery and internal hemorrhage, and also used as an abortive and for menstrual pain relief. The leaves were used for scrofulous diseases. The flowers contribute to a distinctive Kāmahi honey in some regions. The leaves were used to line the graves of the dead, representing the spirit of Tane. Kāmahi is one of New Zealand's most common forest trees, forming a graceful, often multi-stemmed crown. It produces abundant creamy-white flower racemes that are a valuable nectar source for insects and birds. It is resilient, adaptable, and a reliable nurse/canopy tree in restoration plantings.
Bonus Tip
Train a single leader in the first two seasons if a tall, straight trunk is desired; in restoration blocks, allow natural branching for faster canopy closure. Where possums are present, temporary foliage guards dramatically improve establishment.
