Milk Tree
Paratrophis banksii native plants index
Milk Tree (scientific name: Paratrophis banksii) Milk Tree is a small native tree with distinctive serrated leaves and milky sap. It produces small greenish flowers and orange berries, making it an important food source for native birds in coastal and lowland forests. Explore more in the native plants index.
Plant Description
Botanical Features
Milk Tree (Paratrophis banksii), also known by its Mori name ewekuri or as the large-leaved milk tree, is a robust tree or large shrub endemic to New Zealand. It can grow up to 12 meters tall, typically featuring a broad canopy crown and a trunk up to 0.8 meters in diameter with dark brown bark. The common name "milk tree" comes from the milky sap it exudes when cut or damaged. Its leaves vary between juvenile and adult stages. Juvenile plants have variable leaves, 20-60 - 10-30 mm, that are dark green above and paler beneath, elliptic-oblong, with finely to deeply crenate or deeply lobed margins. Adult leaves are larger, 35-85 - 20-35 mm, dark green to yellow-green, paler underneath, and typically ovate to broadly ovate with crenate margins. The leaves are net-veined with a toothed edge. It produces small, grey-green flowers in clusters of long spikes. These are followed by fleshy, red, drupaceous fruits that can be up to 65 mm in diameter.
Quick Facts
Overview
| Scientific Name | Paratrophis banksii |
|---|---|
| Height | 4-8 m |
| Spread | 3-5 m |
| Water Needs | Low to moderate |
| Light | Partial shade to full sun |
| Frost Tolerance | Moderate |
| Salt Tolerance | Poor |
| Growth Rate | Moderate |
| Lifespan | Long-lived |
Climate Best Suited to
Regional climate suitability across major New Zealand cities.
Regional Suitability
| City | Climate Suitability |
|---|---|
| Whangārei | Ideal |
| Auckland | Ideal |
| Hamilton | Ideal |
| Tauranga | Ideal |
| Rotorua | Ideal |
| Gisborne | Ideal |
| New Plymouth | Ideal |
| Napier | Ideal |
| Whanganui | Ideal |
| Palmerston North | Ideal |
| Wellington | Ideal |
| Nelson | Ideal |
| Christchurch | Ideal |
| Dunedin | Ideal |
| Invercargill | Ideal |
Natural Habitat
Paratrophis banksii, also known as ewekuri or large-leaved milk tree, is endemic to New Zealand and thrives in coastal and lowland forests, typically at elevations between 0 and 200 meters above sea level. This tree prefers deep, fertile soils, and larger specimens are often found on alluvial terraces. On offshore islands, it demonstrates a greater tolerance for drier conditions and skeletal soils. In these island environments, it can be found on steep cliff faces, rock ledges, or as stunted shrubs on cobble and boulder beaches.
Its distribution includes the North Island, primarily in easterly regions from Kaitaia to East Cape, Waikato, and northern Hawke's Bay, including the islands of the Hauraki Gulf. It also appears in Horowhenua to Wellington and the western side of Wairarapa. In the South Island, it is found in northern areas such as the Marlborough Sounds (mainly on islands), Abel Tasman National Park, and eastern Golden Bay. While it may have once been more widespread, its current distribution is often sparse, with significant populations mainly found on rodent-free offshore islands.
Plant Conservation
Conservation
Paratrophis banksii, also known as ewekuri, large-leaved milk tree, or tūrepo, is a plant species endemic to New Zealand. As of 2023, its conservation status is classified as "At Risk - Relict." Historically, Paratrophis banksii was more widespread, but its current distribution is sparse, with it rarely being common except on rodent-free offshore islands. Major threats to the species include browsing by introduced pests (possums and goats) and rodent predation, which consumes fruit, seeds, and emerging seedlings. In isolated mainland remnants, the dioecious nature of the species can lead to a sex imbalance, hindering reproduction. Despite these threats, conservation efforts and natural responses have shown positive results. Successful eradication of rodents on offshore islands has led to the rapid re-establishment and recovery of Paratrophis banksii populations. The plant is easily grown from fresh seeds and can be propagated from semi-hardwood cuttings. It is a fast-growing tree that can be used as a specimen or hedge and has been planted for reforestation.
Growing Requirements
Soil Requirements
Prefers moist, wellâdrained, fertile forest soils with organic matter; avoid chronic waterlogging.
Light Requirements
Light shade to full sun with shelter; juvenile plants appreciate nurse canopy.
Water Requirements
Consistent moisture during establishment; moderate thereafter.
For Milk Tree (Paratrophis banksii), choose a site with partial shade to full sun and soil that is low to moderate. Incorporate composted organic matter to improve structure and drainage. Plant with the crown or root collar at soil level, then apply a 5-8â¯cm mulch to moderate temperature, conserve moisture, and suppress weeds. Protect young plants from extremes while establishing and consider the stated frost tolerance (moderate) when siting near exposure or cold air drains.
Planting Guide
Milk Tree (Paratrophis banksii) is a robust and adaptable native New Zealand tree that is relatively easy to grow, making it suitable for various planting scenarios, including hedging, riparian plantings, and forest restoration. Its resilience and ecological value make it a rewarding addition to any native garden.
1. Site Selection and Habitat:
- Natural Habitat: This tree naturally occurs in coastal and lowland forests, typically between 0 and 200 meters above sea level. It prefers deep, fertile soils but can also tolerate drier conditions and skeletal soils, especially on offshore islands where it may be found on cliff faces or rock ledges.
- Light: Milk Tree prefers full sun for optimal growth, though it can tolerate some partial shade.
- Shelter: While adaptable, it thrives best in conditions that offer some shelter from the harshest winds, especially when young.
- Climate: It is highly adaptable to various New Zealand climate conditions, tolerating frost, wind, and drought. It is particularly well-suited for exposed sites and challenging garden conditions.
2. Soil Requirements:
- Preferred Soil: The tree prefers deep, free-draining, and fertile soil.
- Adaptability: It is adaptable to a wide range of soil types, including clay, loam, and sandy soils, and can tolerate poor soil conditions. Good drainage is crucial to prevent root rot.
3. Planting:
- When to Plant: The best time to plant Milk Tree is during the cooler months, from autumn to early spring, to allow root establishment before summer.
- Preparation: Prepare the planting site by removing weeds and amending the soil with organic matter to improve fertility and drainage.
- Depth: Dig a hole that is twice the width of the root ball and to the same depth. Plant the tree at the same depth as it was in its original container.
- Watering: Water thoroughly immediately after planting to settle the soil and eliminate any air pockets.
- Spacing: For hedging or group plantings, space plants about 1.5 to 2 meters apart. For specimen trees, allow at least 4-5 meters for its mature spread.
4. Care and Maintenance:
- Establishment: Once established, Milk Tree requires minimal care. It is very drought tolerant after establishment.
- Watering: Monitor soil moisture levels and provide water during extended dry periods.
- Fertilizing: If needed, apply a light, balanced fertilizer in spring to promote healthy growth.
- Pruning: This is a fast-growing tree that responds well to clipping, making it suitable for use as a hedge. Minimal pruning is generally needed, mainly for tidying up broken branches or shaping.
- Pest and Disease: Regularly inspect plants for any signs of pests or diseases.
Ecological Role
Paratrophis banksii serves as a cornerstone species in New Zealand's coastal and lowland forest ecosystems, playing crucial ecological roles that extend far beyond its impressive stature as a canopy tree reaching 9-12 meters tall. This endemic tree represents an important component of New Zealand's unique biogeography, supporting diverse wildlife communities while demonstrating remarkable adaptability across varied habitat types from fertile alluvial terraces to challenging coastal cliff environments.
Coastal and Lowland Forest Foundation
- Canopy structure provider: Large mature trees create essential upper-story habitat in coastal and lowland forests, providing nesting sites and shelter for native birds while contributing to the complex vertical structure that characterizes healthy New Zealand forest ecosystems.
- Alluvial ecosystem specialist: Thrives on fertile alluvial terraces where it forms part of the dynamic riverside forest communities, helping to stabilize banks while creating habitat complexity that supports diverse flora and fauna.
- Soil development facilitator: Substantial leaf drop and root systems contribute significant organic matter to forest floors, building soil structure and fertility essential for supporting understory plant communities and soil-dwelling invertebrates.
- Microclimate creation: Dense canopy coverage creates cooler, more humid microclimates beneath trees, enabling moisture-sensitive species to establish and thrive while moderating temperature extremes.
Island Ecosystem Adaptability
- Coastal resilience specialist: Demonstrates remarkable adaptability on offshore islands where it tolerates drier conditions and skeletal soils, often colonizing challenging sites including steep cliff faces and rock ledges where few other trees can survive.
- Pioneer establishment capabilities: Ability to establish on cobble and boulder beaches as stunted shrubs provides crucial initial vegetation cover that facilitates succession toward more complex plant communities.
- Salt tolerance benefits: Natural adaptation to coastal conditions enables survival in salt-influenced environments, creating protected zones that enable less salt-tolerant species to establish inland from coastal margins.
- Wind resistance value: Robust growth form and adaptation to exposed island conditions provide natural windbreak functions that protect other vegetation and create stable habitat zones.
Wildlife Habitat and Resource Provision
- Native bird sanctuary: Large trees with dense branching provide excellent nesting and roosting sites for various native bird species, while the mature forest habitat supports the complex food webs essential for avian biodiversity.
- Invertebrate habitat complexity: Bark crevices, leaf litter, and canopy structure create diverse microhabitats for native invertebrates, supporting species that form the base of forest food chains and pollination networks.
- Fruiting resource provision: Small fruits provide seasonal food resources for native birds and other fauna, contributing to the complex network of food relationships that maintain forest ecosystem function.
- Nectar source potential: Flowering provides nectar resources for native pollinators, supporting the pollination services essential for maintaining plant diversity in forest ecosystems.
Conservation and Restoration Ecology
- Restoration project value: Active planting on islands like Mana Island demonstrates its importance for reforestation efforts, where fast growth and adaptability make it valuable for rapidly establishing forest structure.
- Endemic species preservation: As an endemic tree representing over 30% of New Zealand's threatened or uncommon plants, its cultivation and protection contribute to maintaining the unique genetic heritage of New Zealand flora.
- Habitat connectivity: Distributed across both North and South Islands from coastal to inland sites, it provides habitat connectivity that enables wildlife movement and genetic exchange across fragmented landscapes.
- Seed dispersal networks: Fruits attract birds that disperse seeds to new locations, facilitating natural forest regeneration and genetic diversity maintenance across suitable habitat areas.
Ecosystem Services and Resilience
- Carbon sequestration: Fast growth rate and substantial mature size make it an effective carbon sink, storing significant amounts of atmospheric carbon in both above-ground biomass and soil organic matter.
- Erosion control specialist: Root systems effectively stabilize soils on slopes and coastal areas, preventing erosion while maintaining habitat integrity during storm events and high rainfall periods.
- Water cycle regulation: Canopy interception and transpiration contribute to local water cycle regulation, moderating runoff and maintaining consistent moisture levels that benefit entire forest communities.
- Climate resilience provider: Drought tolerance once established and adaptability to various soil types provide ecosystem stability during climate fluctuations and environmental stress periods.
Forest Succession and Dynamics
- Succession facilitation: Fast-growing nature enables rapid colonization of disturbed areas, quickly re-establishing forest structure that facilitates the return of slower-growing species and complex forest communities.
- Disturbance recovery: Ability to establish on varied soil types and challenging sites makes it valuable for natural recovery following storms, landslides, or other natural disturbances.
- Genetic diversity maintenance: Populations across diverse habitats from fertile lowlands to challenging coastal sites maintain genetic diversity essential for species adaptation and long-term ecosystem resilience.
- Edge effect mediation: Tolerance for challenging conditions makes it effective at forest edges where it buffers interior forest communities from external environmental stresses.
Through its multiple ecological functions and remarkable adaptability, P. banksii demonstrates the critical importance of endemic tree species in maintaining the integrity and resilience of New Zealand's unique forest ecosystems across diverse environmental conditions.
Uses & Significance
Practical Applications
Latexâbearing âmilk treeâ with ecological value for forest restoration; fruits feed birds; dense canopy provides shade.
Raise Milk Tree from seed collected when ripe, or by semiâhardwood cuttings set under intermittent mist. Use sharp, diseaseâfree material and maintain moderate warmth and bright, indirect light for rooting.
Landscaping & Design
Paratrophis banksii emerges as an exceptional choice for contemporary New Zealand landscaping, offering versatility that bridges formal design requirements with ecological restoration goals. This endemic milk tree combines rapid establishment with striking architectural form, making it invaluable for both residential gardens and large-scale landscape projects seeking authentic native character with practical performance benefits.
Specimen Tree Applications
- Architectural presence: Fast-growing habit allows rapid development of substantial canopy structure, reaching 9-12 meters to create impressive focal points that establish immediate landscape impact in new developments or garden renovations.
- Seasonal interest provision: Dark green net-veined leaves with distinctive toothed edges provide year-round foliage appeal, while bright yellow flower clusters from September to November followed by vibrant red-orange fruits create seasonal color highlights.
- Adaptable scale management: Natural growth flexibility allows cultivation as large shrub for smaller spaces or full canopy tree for expansive landscapes, providing design scalability across diverse project requirements.
- Unique textural contribution: Characteristic milky sap and robust branching structure offer distinctive textural elements that complement other native species while providing strong architectural backbone for mixed plantings.
Hedging and Screening Excellence
- Rapid privacy establishment: Fast growth rate combined with excellent response to clipping enables quick development of effective privacy screens, windbreaks, and property boundaries without extended establishment periods.
- Formal hedging adaptability: Dense branching pattern and tolerance for regular pruning make it ideal for formal hedge applications where precise shape control and consistent appearance are essential design requirements.
- Wind protection capabilities: Natural coastal adaptation and robust growth form provide excellent windbreak functionality, protecting more delicate plantings while creating sheltered microclimates for garden development.
- Low-maintenance screening: Once established drought tolerance reduces ongoing irrigation requirements, while natural disease resistance minimizes maintenance interventions for sustainable screening solutions.
Water-Wise Garden Design
- Drought-resilient establishment: Once established, exceptional drought tolerance makes it perfect for water-wise landscaping initiatives, reducing irrigation demands while maintaining lush appearance during dry periods.
- Challenging site specialization: Demonstrated ability to thrive on skeletal soils and steep sites extends design possibilities to difficult locations where other species struggle, including coastal exposures and poor drainage areas.
- Climate-adaptive performance: Natural adaptability to varying moisture conditions from coastal to inland environments provides reliable performance across New Zealand's diverse climatic zones.
- Sustainable landscape integration: Minimal water requirements after establishment align with contemporary sustainable design principles while supporting native ecosystem restoration goals.
Native Garden Integration
- Ecosystem restoration backbone: Fast establishment and robust nature make it ideal for initial plantings in restoration projects, providing shelter and structure that facilitates establishment of slower-growing native species.
- Wildlife habitat creation: Fruits attract native birds while dense canopy provides nesting sites, creating active wildlife corridors that enhance garden biodiversity and ecological connectivity.
- Cultural landscape authenticity: Endemic status and traditional Māori uses (ewekuri, tūrepo) provide authentic cultural connections that strengthen sense of place in contemporary New Zealand landscapes.
- Forest succession facilitation: Natural role as colonizing species makes it valuable for staged planting programs where it establishes protective canopy for subsequent understory and forest floor species introduction.
Coastal and Challenging Site Applications
- Coastal tolerance specialist: Natural adaptation to coastal conditions including salt exposure and wind provides reliable performance in challenging seaside locations where many species fail to establish.
- Steep site stabilization: Ability to establish on cliff faces and rock ledges makes it valuable for erosion control and slope stabilization projects where both function and aesthetic appeal are required.
- Exposed site resilience: Wind tolerance and robust growth form enable successful cultivation in exposed locations, creating sheltered areas for additional plantings and garden development.
- Poor soil adaptation: Demonstrated success on skeletal soils extends planting possibilities to sites with challenging growing conditions, reducing need for extensive soil amendment or replacement.
Design Implementation Guidelines
- Spacing considerations: For hedging applications, space plants 1.5-2 meters apart for dense screen development; for specimen use, allow 4-5 meters for full canopy development without crowding adjacent plants.
- Companion planting synergies: Pairs effectively with other coastal natives like Coprosma species and Griselinia for mixed screens, or with understory ferns and ground covers for naturalistic forest edge effects.
- Seasonal maintenance planning: Primary pruning should occur in late winter before spring growth, with light trimming throughout growing season to maintain desired hedge shape and size.
- Long-term performance optimization: Initial establishment care with regular watering for first 12-18 months ensures rapid root development, after which natural drought tolerance provides low-maintenance performance for decades.
Through its combination of rapid establishment, architectural presence, and exceptional adaptability to challenging conditions, P. banksii provides landscape designers with a reliable native solution that delivers both immediate impact and long-term performance across diverse New Zealand environments.
Seasonal Care Calendar
Spring
Plant and mulch; weed control.
Summer
Deep water in drought; check ties.
Autumn
Reduce watering; light tidy.
Winter
Sanitation pruning on fine days.
Pruning & Maintenance
Techniques and Timing
Minimal pruning required; remove dead/damaged wood and crossing branches.
Prune Milk Tree lightly to maintain structure; remove damaged shoots and avoid hard cuts on older wood.
How to Grow Milk Tree
Milk Tree is a small native tree with distinctive serrated leaves and milky sap. It produces small greenish flowers and orange berries, making it an important food source for native birds in coastal and lowland forests. This resilient tree is highly valued for its ecological importance and its role in supporting native biodiversity. Understanding its propagation methods is key to successfully growing this important species.
From Seed
Propagating Milk Tree from fresh seed is a viable method, though it requires careful handling and specific conditions. Collect ripe orange berries in autumn. Extract the seeds from the fleshy pulp and clean them thoroughly. Sow the seeds in a well-draining seed-raising mix, lightly covering them. Maintain consistent moisture in the seed tray and keep it in a warm, shaded location until germination. Germination can take several weeks to months. Once seedlings have developed a few true leaves, they can be potted into individual containers and grown in a sheltered environment before planting out.
From Cuttings
Semi-hardwood cuttings are a possible method for propagating Milk Tree, though success rates can be variable. Take 10-15 cm cuttings from healthy, semi-hardwood stems 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). Keep the cuttings in a warm, humid environment, out of direct sunlight, perhaps under a plastic dome or in a propagator. Rooting typically occurs within 8-12 weeks. Once rooted, the new plants can be potted on and grown in a sheltered environment until they are ready for planting.
Pests & Diseases
Paratrophis banksii demonstrates remarkable natural resilience to most diseases, with its primary health challenges stemming from invasive mammalian pests rather than pathological issues. Understanding these specific threats and implementing appropriate management strategies ensures healthy establishment and long-term survival, particularly in mainland environments where pest pressure significantly exceeds that found on rodent-free offshore islands where this species thrives naturally.
Primary Pest Threats
- Possum browsing damage: Brushtail possums heavily browse foliage, bark, and shoots, causing defoliation and structural damage that weakens trees and reduces vigor. Repeated browsing prevents normal canopy development and can ultimately lead to tree decline or death.
- Goat impact severity: Feral goats cause extensive damage through aggressive browsing of leaves, bark stripping, and trampling around root zones. Their feeding patterns often remove entire branch systems and can girdle trunks, resulting in rapid tree mortality.
- Rodent fruit and seed predation: Rats and mice consume fruits, seeds, and emerging seedlings with devastating efficiency, preventing natural regeneration and disrupting reproductive cycles essential for population maintenance.
- Seedling establishment interference: Ground-dwelling rodents actively seek out and consume newly emerged seedlings, effectively preventing natural recruitment and requiring protective measures for successful regeneration programs.
Environmental Stress Factors
- Drought stress vulnerability: While established trees demonstrate excellent drought tolerance, newly planted specimens require consistent moisture during their first 12-18 months. Extended dry periods without supplemental irrigation can cause establishment failure and increased susceptibility to other stresses.
- Waterlogging sensitivity: Poor drainage leading to prolonged soil saturation creates conditions favorable for root rot pathogens, particularly Phytophthora species that can cause rapid decline in previously healthy trees.
- Wind damage exposure: Young trees in exposed locations may experience branch breakage, trunk lean, or root disturbance during severe weather events, requiring adequate shelter or staking during establishment phases.
- Transplant shock risks: Improper planting techniques, inadequate root preparation, or extreme weather during planting can cause transplant shock, manifesting as leaf drop, dieback, or complete establishment failure.
Potential Fungal Disease Issues
- Phytophthora root rot: Various Phytophthora species can affect milk trees in poorly drained soils or during extended wet periods, causing root decay, collar rot, and crown dieback. Prevention through proper drainage and soil management is more effective than treatment.
- Armillaria root disease: Native Armillaria species may attack stressed or weakened trees, particularly those compromised by other factors. This fungal pathogen spreads through root contact and can cause gradual decline over several growing seasons.
- Sooty mold development: Secondary infection following honeydew-producing insect infestations can result in black sooty mold covering foliage, reducing photosynthetic capacity and overall tree vigor.
- Leaf spot diseases: Various fungal pathogens may cause minor leaf spotting during humid conditions, though these typically have minimal impact on overall tree health and resolve with improved air circulation.
Management and Prevention Strategies
- Integrated pest management: Implement comprehensive pest control programs targeting possums, goats, and rodents through trapping, fencing, and coordination with local pest management initiatives to reduce browsing pressure and protect natural regeneration.
- Protective establishment techniques: Use tree guards, mesh protection, or temporary fencing around newly planted specimens to prevent pest damage during vulnerable establishment periods when trees are most susceptible to browsing injury.
- Optimal site preparation: Ensure excellent drainage through soil amendment or raised planting areas to prevent waterlogging conditions that encourage root rot pathogens while maintaining adequate moisture retention for healthy growth.
- Regular monitoring protocols: Conduct systematic inspections for early detection of pest damage, disease symptoms, or environmental stress indicators, enabling prompt intervention before problems become severe or irreversible.
Cultural Control Practices
- Proper spacing implementation: Maintain adequate spacing between trees to promote good air circulation, reduce humidity levels that favor fungal diseases, and prevent overcrowding that increases competition stress and susceptibility to problems.
- Mulching strategy optimization: Apply organic mulch to conserve soil moisture, moderate temperature extremes, and suppress weeds, while avoiding direct contact with tree trunks to prevent collar rot and rodent harboring conditions.
- Irrigation management precision: Provide deep, infrequent watering during establishment, gradually reducing frequency as drought tolerance develops, while avoiding both water stress and oversaturation that predispose trees to root diseases.
- Pruning hygiene maintenance: Use clean, sharp tools for any pruning activities, making proper cuts that heal quickly and avoid creating entry points for pathogens, while removing any damaged or diseased material promptly.
Recovery and Restoration Success
- Rapid response to pest removal: Documented evidence from island restoration projects demonstrates that milk trees respond dramatically to rodent eradication, quickly re-establishing healthy populations and natural regeneration cycles when pest pressure is eliminated.
- Natural disease resistance: Inherent robustness and adaptation to New Zealand conditions provide strong natural resistance to most disease problems, with healthy trees rarely experiencing significant pathological issues under proper growing conditions.
- Ecosystem restoration benefits: Healthy milk tree populations contribute to overall ecosystem resilience, creating habitat conditions that support beneficial insects and natural enemies of potential pest species.
- Long-term durability advantages: Once established beyond initial vulnerable phases, mature trees demonstrate exceptional longevity and continued health with minimal intervention, providing decades of reliable landscape performance.
Through proactive pest management and attention to optimal growing conditions, P. banksii can be successfully established and maintained as a robust, healthy component of New Zealand native landscapes with minimal ongoing health concerns.
Cultural Significance
Paratrophis banksii, also known by its Māori name ewekuri or as the large-leaved milk tree, is a plant species endemic to New Zealand.
The milky sap the tree exudes when cut or damaged is the origin of its common name "milk tree." Historically, early European colonists even used this milky juice as a substitute for milk in tea.
While the plant is known by its Māori name "ewekuri," there is limited specific information regarding its broader cultural significance to Māori beyond the naming. The name "banksii" refer to Sir Joseph Banks, a British naturalist on Cook's first voyage to New Zealand.
Bonus Tip
The common name "milk tree" comes from the milky sap it exudes when its bark is cut or damaged. Historically, early colonists in New Zealand even used this milky juice as a substitute for milk in tea!
