Oliver's Greenhood (Pterostylis oliveri) hero image

Oliver's Greenhood

Pterostylis oliveri

Not Threatened

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Oliver's greenhood (Pterostylis oliveri) is a terrestrial orchid found only in the western South Island, from North-west Nelson south to about Arthur's Pass National Park. Plants grow 10 to 38 cm tall with four to six spreading leaves and a single large green flower finely striped with white, opening in December and January. It favours montane forest and subalpine scrub, often along streams or in deep drifts of partly rotted leaf litter. It is closely related to Pterostylis patens but tends to sprawl rather than stand stiffly upright. It is ranked Not Threatened but is difficult to grow and should be left in the wild. Explore more native flowering plants in our native plant guide.

Oliver's Greenhood (Pterostylis oliveri) in its natural habitat
Image credit: Oliver's Greenhood (Pterostylis oliveri) - photo by Wikipedia contributors, via Wikipedia

Plant Description

Pterostylis oliveri is a tuberous ground orchid 10 to 38 cm tall, with a smooth stem about 2 mm thick. It carries four to six spreading leaves; the lower ones are oval to broadly elliptic, about 5 to 10 cm long and 2 to 3 cm wide, and the upper leaves become progressively more pointed and stalkless.

The solitary flower has a dark green hood (galea) finely striped with white, the white stripes widening toward the back of the hood. The dorsal sepal stands about 3 to 4 cm tall and ends in a long narrow tip, while the lateral sepals diverge at a narrow angle and have very long lobes. The narrow triangular labellum is arched and protrudes from the flower, and the column is shorter than the labellum.

Its closest relative is Pterostylis patens, which has a similar striped flower. Oliver's greenhood is usually separated by its often decumbent or sprawling habit, compared with the stiffly erect growth of P. patens, and by its western South Island range.

Quick Facts

Pterostylis oliveri quick facts
Scientific Name Pterostylis oliveri
Height 0.1-0.38 m in flower
Spread Single plants or loose groups
Water Needs Constantly moist leaf litter
Light Shade to semi-shade under forest or scrub
Frost Tolerance High; a montane to subalpine species
Salt Tolerance Low; an inland mountain plant
Growth Rate Seasonal; regrows from a tuber
Lifespan Perennial (tuberous)

Climate Best Suited to

Suits the cool, very wet montane climate of the western South Island, with high rainfall, mild summers and cold winters. It would struggle in warm or dry lowland gardens.

Regional Suitability

City suitability for Pterostylis oliveri
City Climate Suitability
Auckland Low
Wellington Low
Christchurch Low
Dunedin Low

Plant Habitat

Oliver's greenhood is endemic to the western South Island. Its range runs from North-west Nelson south to about Arthur's Pass National Park, taking in the mountains of Kahurangi and the ranges of Buller and Westland.

It grows in montane forest and subalpine scrub, rarely above 1200 m. It is often found along stream sides or under shrubs, growing through dense drifts of partially decomposed leaf litter where moisture stays high year round.

Growing Requirements

Soil Requirements

Its tubers sit in deep, loose layers of rotting leaf litter over forest soil.

  • Deep, moist, humus-rich leaf litter
  • Cool, acidic forest soils
  • Loose surface layers that never dry out completely

Light Requirements

It grows beneath forest canopy or under subalpine shrubs, out of direct sun.

  • Shade to semi-shade
  • Often at the sheltered edges of streams

Water Requirements

The western South Island mountains receive very high rainfall, and the plant favours the dampest spots within them.

  • Needs consistently moist conditions while in growth
  • Stream margins and damp hollows are typical sites

Planting and Establishing

Oliver's greenhood is not commercially available, and NZPCN describes it as difficult to grow, stating that it should not be removed from the wild.

The best way to support it is to protect the leaf litter and shrubs where it grows. Avoid raking or clearing litter in forest margins where greenhoods occur.

Ecological Role

Like other greenhoods it has a hinged, sensitive labellum that tips a visiting insect into the hood, forcing it past the pollen on its way out. Greenhoods are generally pollinated by small flies such as fungus gnats; the specific pollinator of this species is not documented in the sources consulted.

Its dust-like seed depends on soil fungi to germinate, and the plant relies on its underground tuber to survive the dormant season. Thick leaf litter in damp montane forest supplies both the fungi and the moisture it needs.

Uses & Significance

Garden Uses

It is not a garden plant, since it is difficult to cultivate and should not be taken from the wild.

  • Best enjoyed in the forests of Kahurangi, Paparoa and Arthur's Pass
  • Of interest to orchid photographers in midsummer
  • Not available from nurseries

Ecological Value

It is part of the rich ground orchid flora of western South Island beech and montane forest.

  • An endemic orchid restricted to the western South Island
  • Indicates intact, undisturbed forest floor and leaf litter
  • Provides a trap flower resource for small flies

Landscaping Uses

It has no landscaping use. Its value lies in the natural settings where it grows, often in groups along shaded stream banks among mosses and ferns.

In private forest remnants within its range, leaving leaf litter, logs and shrubs in place and keeping stock out are the most useful ways to keep greenhoods present.

Seasonal Care Calendar

Spring

Leaves emerge from the tubers in the damp forest floor as the mountains warm.

  • Avoid trampling stream margins
  • Watch for leafy shoots in deep litter

Summer

Flowering runs through December and January, when the large striped hoods are easy to spot.

  • Photograph rather than pick
  • Look along streams and under subalpine shrubs

Autumn

Fruiting continues from January to April, and capsules release their fine seed.

  • Leave seed capsules undisturbed
  • Foliage begins to die back

Winter

The plant rests as an underground tuber beneath cold, often snowy montane forest.

  • No visible growth
  • Leaf litter protects the tubers

When to Prune and How Much

No pruning is required. The leaves and flower stem wither naturally after fruiting.

In the wild, leave old stems and surrounding litter alone, since the litter layer is the plant's habitat.

How to Grow Oliver's Greenhood

NZPCN rates Pterostylis oliveri as difficult to propagate and says it should not be removed from the wild, and it is not commercially available. No published propagation protocol specific to this species was found in the sources consulted. The notes below describe how specialist growers approach greenhoods in general, for anyone holding legally obtained material for research or conservation. Expect slow progress and frequent failures, because greenhoods depend on soil fungi and very particular moisture conditions, and wild plants are best left where they are.

From Seed

Greenhood seed is extremely fine and germinates only in association with suitable mycorrhizal fungi. Growers usually scatter seed into pots that already support established greenhoods, so that the fungus is present.

  1. Collect capsules from cultivated plants as they start to yellow in late summer
  2. Sprinkle the seed on the surface of a pot holding established greenhoods
  3. Keep the pot cool, shaded and evenly moist
  4. Leave seedlings undisturbed for at least a year before checking for tubers

By Tuber Division

Many greenhoods produce extra tubers that can be separated while dormant. Whether Oliver's greenhood does so readily in cultivation is not recorded in the sources consulted.

  1. Wait until the foliage has completely withered in late autumn
  2. Gently remove the potting mix and look for small daughter tubers
  3. Replant each tuber shallowly in a free-draining, leafy mix
  4. Keep it cool and only lightly moist until new shoots appear in spring

Pests & Diseases

No specific pests are recorded for this species. Slugs and snails commonly graze greenhood leaves and flowers, and browsing by deer could damage plants in accessible forest.

In cultivation, rot from stale, waterlogged mix is the most likely cause of failure.

Cultural Significance

Greenhood orchids are known in te reo Māori as tutukiwi, but no Māori name or use specific to Pterostylis oliveri is recorded in the sources consulted.

Donald Petrie, an Otago-based school inspector and botanist, described the species in 1894 and named it after Professor Daniel Oliver of the Royal Botanic Gardens, Kew, in thanks for his assistance.

Bonus Tip

To find Oliver's greenhood, walk a montane stream-side track in Kahurangi or near Arthur's Pass during December or January and scan the deep leaf litter under shrubs. A sprawling stem with a white-striped green hood points to this species rather than the stiffly upright Pterostylis patens.

Plant Conservation

Pterostylis oliveri is ranked Not Threatened (2023). Much of its range lies within public conservation land, including Kahurangi, Paparoa and Arthur's Pass National Parks.

Because it relies on undisturbed forest floor, the main things that help are controlling browsing animals, keeping visitors on tracks and never collecting plants from the wild.

Frequently Asked Questions

Where does Oliver's greenhood grow?

It is endemic to the western South Island, from North-west Nelson to about Arthur's Pass National Park, in montane forest and subalpine scrub rarely above 1200 m.

How do you tell Pterostylis oliveri from Pterostylis patens?

NZPCN says the two are close, but Oliver's greenhood is often decumbent or sprawling, while Pterostylis patens holds itself consistently and stiffly erect.

Who is Oliver's greenhood named after?

Donald Petrie described it in 1894 and named it after Professor Daniel Oliver of Kew Gardens, who had helped Petrie with his work.

When does Oliver's greenhood flower?

It flowers in December and January, with seed capsules ripening from January to April.

Sources and Further Reading

The botanical, growing, and conservation details for Oliver's Greenhood (Pterostylis oliveri) on this page draw on the New Zealand plant references below. Consult them for full technical records and the latest distribution data.