Silver Pine

Manoao colensoi

Not Threatened

This native plant, known as Silver Pine (scientific name: Manoao colensoi ), is a remarkable species endemic to New Zealand. It is characterized by its unique features, ecological role, and cultural significance. This comprehensive guide provides detailed information on its care, propagation, and importance within the New Zealand ecosystem. Understanding this plant contributes to the appreciation of our rich biodiversity and heritage, and supports conservation efforts for native trees .

Silver Pine (Manoao colensoi) showing distinctive yellow-green scale-like foliage — Image credit: Silver Pine ( *Manoao colensoi* ) - photo by Wikipedia contributors, via Wikipedia

Plant Description

Identification and Physical Characteristics

Manoao colensoi , commonly known as Silver Pine, Westland Pine, or Manoao in te reo Māori, is the sole species in the monotypic genus Manoao, making it truly unique among New Zealand's conifers. This evergreen conifer grows to heights of 15 meters tall with a trunk diameter up to 1 meter at breast height. Young trees display a distinctive cone shape, while mature specimens develop a tall, moderately spreading crown with yellow-green foliage and branches that weep gracefully at their ends. The juvenile plants exhibit limp needle-like leaves that gradually transform into overlapping yellowish-green scale-like leaves with a prominent ridge or keel on the lower outer surface. The bark is grey-brown and flakes off in thick scales, revealing reddish-brown patches underneath. One of the most remarkable features of this species is its extremely rare ability among conifers to spread via underground stems that produce suckers, ultimately giving rise to new trees; a trait shared only occasionally with another New Zealand genus, Phyllocladus.

Quick Facts

*Manoao colensoi* quick facts
Scientific Name	Manoao colensoi
Height	10-15 m (occasionally up to 20 m)
Spread	3-5 m (can form groves via suckers)
Water Needs	High; prefers consistently moist conditions
Light	Partial shade to filtered sun
Frost Tolerance	Good; hardy to -12°C
Salt Tolerance	Low
Growth Rate	Very slow (0.6-1.7 mm diameter annually)
Lifespan	Very long-lived (several centuries)

Climate Best Suited to

Manoao colensoi thrives in high-rainfall temperate climates typical of New Zealand's western regions. It requires consistent moisture with mean annual precipitation around 3700 mm in its natural habitat. The species tolerates mean annual temperatures of about 11°C and can withstand winter minimums down to -12°C. While naturally occurring in very wet environments, it actually grows faster on well-drained sites with adequate moisture rather than waterlogged soils.

Regional Suitability

City suitability for Silver Pine
City	Climate Suitability
Auckland	Medium
Wellington	High
Christchurch	Low
Dunedin	Medium
Hamilton	Medium
Tauranga	Medium
Nelson	Medium-High
Greymouth	High

Plant Habitat

Natural Occurrence and Ecology

Manoao colensoi is found from North Cape to South Westland and Lake Te Anau, though it is notably absent from large parts of the North Island, eastern South Island, Fiordland, and Stewart Island. In the North Island, it occurs from Te Paki southward, being uncommon in the north but mainly concentrated around the mountains of the Central Volcanic Plateau. In the South Island, it predominantly inhabits westerly areas with high rainfall. The species typically grows in shady situations on older, poorly drained surfaces with leached, infertile soils, particularly in acid swamps and peats, notably the distinctive 'pakihi' lands of the western South Island. As a pioneer species of infertile bogs, it has adapted to thrive where few other trees can compete, though paradoxically it grows best on deep, fertile, well-drained soils when given the opportunity. The species forms part of the complex mosaic of New Zealand's temperate rainforests and plays an important ecological role in colonizing and stabilizing wetland margins.

Growing Requirements

Soil Requirements

Adaptable to various soil types but prefers acidic to neutral pH with good organic content. While naturally found in poorly drained, infertile soils, it performs best in deep, fertile, well-drained conditions with consistent moisture.

Acidic to neutral pH (4.5-7.0)
Rich in organic matter
Well-drained but moisture-retentive
Tolerates poor, peaty soils

Light Requirements

Naturally occurs in shady forest situations. Seedlings are notably shade-tolerant, allowing them to establish under forest canopy. Mature trees benefit from filtered sunlight or partial shade.

Partial shade preferred
Filtered sunlight
Tolerates deep shade when young
Avoid full sun exposure

Water Requirements

Evolved in high-rainfall districts receiving around 3700 mm annually. Requires consistent moisture but not waterlogging. Once established, shows some drought tolerance but grows best with regular water supply.

High water needs
Keep soil consistently moist
Good drainage essential
Mulch to retain moisture

Planting and Establishing

Establishment Guidance

When planting Manoao colensoi , select a sheltered site with partial shade and protection from strong winds. Prepare a planting hole twice the width of the root ball and amend heavy clay soils with organic matter to improve drainage. Plant at the same depth as the nursery container, ensuring the root collar sits at soil level. Water thoroughly after planting and maintain consistent moisture during establishment. Apply a thick layer of organic mulch around the base, keeping it away from the trunk to prevent rot. Young plants benefit from shade cloth or companion planting with faster-growing natives that provide initial shelter. Due to its very slow growth rate, patience is essential; consider planting multiple specimens to create the grove effect that occurs naturally through suckering. Protect from browsing animals, particularly possums and deer, which can damage young growth. Regular monitoring during the first three years ensures successful establishment, after which the plant becomes remarkably resilient and requires minimal maintenance beyond ensuring adequate moisture during dry periods.

Ecological Role

Biodiversity and Ecosystem Impact

Manoao colensoi plays a specialized ecological role as a pioneer species in New Zealand's wetland and forest ecosystems. Its ability to colonize infertile, waterlogged soils makes it crucial for stabilizing bog margins and initiating forest succession in challenging environments. The tree provides important habitat structure in pakihi lands and swamp forests, where its persistent canopy offers shelter for epiphytes, including native orchids and ferns. Birds such as kākā and parakeets feed on its seeds, while the dense foliage provides nesting sites for smaller forest birds. The unique suckering habit creates interconnected grove systems that increase structural complexity and microhabitat diversity. As one of only twenty native conifer species in New Zealand, and the sole representative of its genus, Silver Pine contributes unique genetic diversity to the country's flora. Its slow growth and longevity mean individual trees become increasingly valuable ecological anchors over centuries, supporting complex communities of associated species including lichens, mosses, and invertebrates that depend on stable, long-lived host trees.

Uses & Significance

Garden Uses

Silver Pine makes an exceptional specimen tree for gardens with suitable conditions. Its distinctive yellow-green foliage, weeping branch tips, and unique growth form create year-round interest. Ideal for woodland gardens, bog gardens, and as a feature in native plant collections.

Specimen tree for large gardens
Woodland and forest gardens
Bog garden feature
Native restoration projects
Conservation plantings

Ecological Value

Provides critical ecosystem services including soil stabilization in wetlands, carbon sequestration over centuries, and habitat for specialized wetland fauna. Seeds provide food for native birds, while the tree supports diverse epiphytic communities.

Seed source for kākā and parakeets
Host for native epiphytes
Wetland stabilization
Long-term carbon storage
Microhabitat provider

Landscaping Uses

In landscape design, Manoao colensoi offers unique aesthetic and ecological value for projects emphasizing native biodiversity and long-term sustainability. Its distinctive form with weeping branch tips and yellow-green foliage provides textural contrast against darker-leaved natives. The tree works exceptionally well in naturalistic woodland plantings, where its slow growth allows for long-term garden stability without frequent maintenance. Consider using it as a focal point in rain gardens or bioswales, where its adaptation to moist conditions proves advantageous. The suckering habit can be utilized to create naturalistic groves over time, providing screening and habitat complexity. For heritage or botanical gardens, Silver Pine represents an important conservation specimen, being one of New Zealand's rarest conifers in cultivation. Partner with other moisture-loving natives like kahikatea, pukatea, and tree ferns to recreate authentic New Zealand forest associations. Its tolerance of shade makes it valuable for underplanting established trees, gradually adding mid-story complexity to developing forest gardens.

Seasonal Care Calendar

Spring

Apply slow-release native plant fertilizer sparingly. Check for new growth and sucker development. Refresh mulch layer to conserve moisture for the growing season ahead.

Light fertilization if needed
Monitor new growth
Refresh organic mulch
Check for pest damage

Summer

Maintain consistent moisture during dry periods. Monitor for stress signs like yellowing foliage. Provide additional shade for young plants during extreme heat.

Deep watering weekly
Monitor soil moisture
Check for heat stress
Maintain mulch cover

Autumn

Ideal planting time for new specimens. Collect seeds if available for propagation. Prepare plants for winter by ensuring good drainage around root zone.

Plant new specimens
Collect ripe seeds
Reduce watering gradually
Clear debris from base

Winter

Silver Pine is frost-hardy but young plants benefit from wind protection. Avoid fertilizing. Monitor drainage to prevent waterlogging during wet weather.

Protect young plants from wind
Ensure good drainage
No fertilization needed
Minimal maintenance required

When to Prune and How Much

Manoao colensoi requires minimal pruning due to its naturally attractive form and slow growth rate. Any necessary pruning should be done in late winter or early spring before new growth begins.

Remove only dead or damaged branches
Avoid heavy pruning which can spoil natural form
Thin crowded suckers if grove management needed
Clean cuts with sharp, sterilized tools
Never top or severely reduce main leader

The tree's slow growth means pruning decisions have long-lasting consequences. Focus on maintaining the natural weeping character of branch tips and the overall pyramidal to columnar shape. If managing suckering growth, selectively remove unwanted shoots at ground level rather than attempting to control through pruning. Remember that each cut on this slow-growing species may take years to heal completely, so conservative pruning approaches work best. For specimen trees, the goal should be to enhance rather than alter the natural form, removing only what is necessary for tree health and structural integrity.

How to Grow Silver Pine

Cultivating Silver Pine ( Manoao colensoi ) is a rewarding endeavor for any gardener interested in New Zealand's unique flora. This species can be propagated through several methods, each requiring specific conditions to ensure healthy growth and establishment. Successful propagation depends on mimicking the plant's natural environment and providing consistent care during the early stages of development.

From Seed

Propagation from seed is often the most effective way to produce a large number of Silver Pine plants. Seeds should be collected when they are fully mature, typically in autumn when cones begin to open. Freshly collected seeds generally have higher germination rates than those that have been stored for long periods. Germination can be very slow and erratic, sometimes taking several months, so patience is essential. The seeds benefit from a period of cold stratification to break dormancy.

Sow fresh seeds in a well-draining, acidic seed-raising mix kept consistently moist but not waterlogged. Use containers with excellent drainage.

Collect ripe seeds from female cones in autumn
Cold stratify for 2-3 months at 4°C
Sow in acidic seed-raising mix
Maintain in cool, shaded conditions
Keep consistently moist using rain or distilled water
Be patient; germination may take 3-12 months

Once germinated, seedlings are slow-growing and should remain in containers for at least two years before transplanting.

From Cuttings

For those wishing to replicate specific characteristics of a parent plant, vegetative propagation via cuttings is the preferred method. This technique ensures that the new plants are genetically identical to the source. Hardwood cuttings taken during winter dormancy usually yield the best results for this species.

Take hardwood cuttings in winter from current season's growth. Use rooting hormone specifically formulated for difficult-to-root conifers.

Select healthy hardwood shoots in winter
Cut 10-15 cm lengths with a heel if possible
Remove lower foliage carefully
Dip in IBA rooting hormone (3000-8000 ppm)
Insert in pumice or perlite mix
Maintain high humidity with bottom heat

Additional Methods

The unique suckering ability of Manoao colensoi offers another propagation opportunity. Root suckers can be carefully separated from the parent plant and grown on independently. This natural characteristic makes it one of the few conifers that can be propagated through division.

Division of root suckers should be done in early spring when the plant is beginning active growth.

Locate healthy suckers with their own root system
Carefully excavate around the sucker
Sever connection to parent with sharp spade
Lift with as much root system as possible
Pot immediately in suitable growing medium
Keep shaded and moist until established

Pests & Diseases

Manoao colensoi is generally resistant to major pests and diseases, benefiting from its adaptation to New Zealand's native conditions. However, young plants can be vulnerable to browsing damage from possums, deer, and goats, which find the foliage palatable. Root rot can occur in poorly drained soils, particularly Phytophthora species, emphasizing the importance of good drainage despite the plant's preference for moist conditions. Scale insects occasionally infest stressed plants, appearing as small brown bumps on stems and foliage. Fungal needle blights may develop in overly humid conditions with poor air circulation. Prevention through proper siting, adequate spacing, and maintaining plant vigor provides the best defense. If pest issues arise, use targeted organic interventions rather than broad-spectrum chemicals that could harm beneficial organisms. Regular monitoring allows early detection and intervention before problems become severe. The slow growth rate means recovery from damage takes considerable time, making prevention particularly important for this species.

Cultural Significance

Manoao colensoi holds important cultural and historical significance in New Zealand. Before European colonization, Māori recognized manoao as exceptionally durable timber, using it for specialized construction where longevity was paramount. The wood's resistance to decay made it valuable for whare (house) foundations and posts in contact with soil. The species is named after William Colenso (1811-1899), a British missionary, printer, botanist, and explorer who collected the type specimen and contributed significantly to documenting New Zealand's flora. The timber gained commercial importance during the colonial period for its strength, durability, and beautiful grain, leading to extensive harvesting. The wood was particularly prized for furniture making, flooring, and weather-exposed construction. Today, with native trees fully protected by law, manoao represents both natural and cultural heritage. Its rarity in cultivation (found in only ten botanical gardens globally according to recent surveys) highlights the importance of conservation efforts. The tree's unique biological characteristics, including its rare suckering ability among conifers, make it scientifically valuable for understanding conifer evolution and adaptation strategies.

Traditional Māori construction material
Historical timber for furniture and building
Scientific importance as monotypic genus
Conservation symbol for wetland forests
Educational value in botanical collections

Bonus Tip

Take advantage of Silver Pine's unique suckering ability by allowing it space to form a natural grove over time. This creates a spectacular landscape feature that mimics its natural growth pattern.

For an authentic forest garden effect, underplant your Manoao colensoi with native ferns like crown fern (Blechnum discolor) and filmy ferns (Hymenophyllum species), along with native sedges that thrive in similar moist, shaded conditions. This combination not only looks natural but also helps maintain the humid microclimate that Silver Pine prefers. Consider installing a rain garden or bog feature nearby to provide the consistent moisture levels that promote optimal growth. Remember that while this tree grows slowly, its longevity means you're creating a legacy planting that will be enjoyed for generations; a true investment in New Zealand's botanical heritage.

Plant Conservation

Conservation Status

Manoao colensoi is currently classified as "Not Threatened" according to the New Zealand Threat Classification System. However, this status doesn't fully reflect the species' conservation challenges. While not immediately threatened with extinction, Silver Pine faces ongoing habitat loss through wetland drainage, conversion of pakihi lands, and climate change impacts on its specialized bog habitats. The species' very slow growth rate and specific habitat requirements make population recovery challenging. Its extreme rarity in cultivation (present in only ten botanical collections worldwide) represents a missed opportunity for ex-situ conservation. The tree's unique biological characteristics, including being the sole species in its genus and one of the few conifers capable of suckering, make it irreplaceable from both ecological and evolutionary perspectives. Conservation efforts should focus on protecting remaining pakihi and wetland forest habitats, establishing ex-situ populations in botanical gardens, and promoting its use in appropriate restoration projects. Home gardeners can contribute by growing this species where conditions permit, helping to maintain genetic diversity outside its natural range.