Pterostylis cernua
Common names
Westland greenhood
Biostatus
Native – Endemic taxon
Current conservation status
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2022-2023 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website. This report includes replaces all previous NZTCS lists for vascular plants. Previous assessments can be found here.
- Conservation status of vascular plants in Aotearoa New Zealand, 2023. 2024. Peter J. de Lange, Jane Gosden, Shannel P. Courtney, Alexander J. Fergus, John W. Barkla, Sarah M. Beadel, Paul D. Champion, Rowan Hindmarsh-Walls, Troy Makan and Pascale Michel Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2023 | At Risk – Naturally Uncommon | Qualifiers: Sp
Category
Vascular
Structural class
Orchids
Flower colours
Green, White
Detailed description
Terrestrial greenhood orchid growing in small colonies of 1–8 plants. Plants dimorphic. Sterile plants 30–60 mm tall, 3–5-leaved; leaves 15–35 × 4–7 mm, dark green to yellow-green, elliptic to elliptic-lanceolate, margins entire or slightly irregular. Flowering plants 60–120 mm tall. Leaves 4–5, 20–65 × 5–7 mm, cauline, erect to spreading; narrowly lanceolate, dark green to yellow-green, sessile, sheathing at base; margins entire; apex acuminate. Pedicel 10–20 mm long, slender. Ovary 9–12 mm, asymmetric, ribbed. Flower solitary, 14–18 mm long, semi-nodding, translucent white and dark green with red-brown suffusions toward galea apex and on lateral sepals. Galea erect and gibbous at the base then leaning forwards before decurving in a shallow curve to the apex. Dorsal sepal ovate-lanceolate in outline then flattened, 25–28 × 11–13 mm, expanded in the proximal ⅓ then sharply narrowed, gradually tapering to the acuminate apex. Lateral sepals erect, loosely embracing galea, leaving a narrow gap to petal margins; conjoined portion 5–7 × 6–7 mm at top, narrowed to 2 mm wide at base, margins inrolled toward apex and tapered into the free points; free points 13–15 mm long, filiform, curved forwards, tips protruding over galea. Petals 17–20 × 3–4 mm, green with a narrow white central area towards the base, apex reddish-brown; obliquely oblong-lanceolate, falcate, acute, flange vestigial. Labellum erect, curved forwards distally, the apex protruding through the sinus in the set position; lamina 7–8 × 2–2.5 mm, dark green with a black-green central callus, narrowly obovate, apex subobtuse, labellum hinge ligulate 3 × 2 mm. Capsules ellipsoid, deeply grooved, yellow-brown to green-brown prior to dehiscence.
Similar taxa
When it was described, P. cernua was said to be part of the P. montana Hatch complex. However, it has little obvious relationship to entities within that species aggregate and is in fact much harder to distinguish from variants within the P. graminea Hook.f. complex. From these it chiefly differs by its somewhat broader and characteristically bunched leaves, and usually smaller (14–18 mm long), distinctly decurved, somewhat nodding narrow (6–7 mm wide) flowers and filiform free points on the lateral sepals. The most widespread form of the P. graminea complex in the South Island prefers drier habitats than P. cernua.
Distribution
Endemic. New Zealand: South Island(West Coast in and around Hokitika, Kumara and Lake Mahinapua). Exact distribution still to be determined as this species was only recognised and described as new in 1997.
Habitat
Lowland (10–40 m a.s.l.) in swampy ground, roadside drains, ditches, margins of peat lakes and fens in sites subject to periodic inundation. Also on poorly drained gley soils overlying infertile, poorly drained gravels stemming from past glacial outwash.
Threats
The type locality is under constant threat from road maintenance and widening. Plants at this site are also at risk from weka predation (the birds plough up plants and eat the orchid tubers). Aside from the extreme vulnerability at this site P. cernua seems secure at the other sites in which it has been found. It is intensively monitored at the most of the known populations and more plants and locations are being discovered each season. These results suggest it is a biologically sparse, possibly widespread and easily overlooked plant. The declines happening at the type locality seem the exception rather than the rule for the species.
Detailed taxonomy
Genus
Family
Synonyms
None (first described in 1997)
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Ecology
Flowering
November–January
Fruiting
December–April
Propagation technique
Difficult—should not be removed from the wild. Basic orchid mix consists of 2 parts medium coarse sand, ideally clean river sand; 2 parts soil, humus or leaf-mould; 1 part weathered sawdust or rotting wood; 1 part granulated bark. For Pterostylis shade of 50% and pots kept evenly moist.
Other information
Etymology
pterostylis: Winged column
cernua: Drooping
Manaaki Whenua Online Interactive Key
Chromosome number
2n = 44
Previous conservation statuses
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2022-2023 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website. This report includes replaces all previous NZTCS lists for vascular plants. Previous assessments can be found here.
- Conservation status of vascular plants in Aotearoa New Zealand, 2023. 2024. Peter J. de Lange, Jane Gosden, Shannel P. Courtney, Alexander J. Fergus, John W. Barkla, Sarah M. Beadel, Paul D. Champion, Rowan Hindmarsh-Walls, Troy Makan and Pascale Michel Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2017 | At Risk – Naturally Uncommon | Qualifiers: Sp
2012 | At Risk – Naturally Uncommon | Qualifiers: Sp
2009 | At Risk – Naturally Uncommon | Qualifiers: EF, DP
2004 | Sparse
Regional conservation statuses
Otago: 2025 | Regionally Threatened – Regionally Critical | Qualifiers: DPR, DPS, DPT, NR, NS, OL, Sp
The regional threat classification system leverages off the national assessments in the NZTCS, providing information relevant for the regional context. Otago conservation status information is sourced from the “Conservation Status of Indigenous Vascular Plants in Otago, 2025” Jarvie S et al. (2025) report.
Referencing and citations
References and further reading
Jones DL, Molloy BPJ, Clements MA. 1997. Six new species of Pterostylis R.Br. (Orchidaceae) from New Zealand. The Orchadian 12: 266–281.
Attribution
Fact Sheet prepared for NZPCN by P.J. de Lange 14 April 2007. Description based on Jones et al. (1997).
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Pterostylis cernua Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/pterostylis-cernua/ (Date website was queried)