Pterostylis irwinii
Common names
greenhood
Biostatus
Native
Category
Vascular
Structural class
Orchids
Flower colours
Green, White
Detailed description
Terrestrial tuberous herb growing in diffuse colonies. Plants dimorphic. Sterile plants 60–100 mm tall; 2–3-leaved; leaves linear, 40–120 × 30–50 mm, dark green, entire acuminate. Flowering plants 150–200 mm tall, stems reddish. Leaves 3–5, cauline, widely spaced, spreading; lamina linear, 60–170 × 4–5 mm, dark green to bronze-green, glossy beneath, sessile, sheathing at base; margins entire; apex acuminate. Pedicel 20 mm long, slender. Ovary linear, 10–13 mm long, ribbed, reddish or red-brown. Flower solitary, 35–45 × 10–12 mm, erect, translucent white and dark green with red to red-brown suffusions in the apex of the galea and lateral sepals; galea shallowly gibbous at the base then erect before bending forwards, the apex erect to obliquely erect, the dorsal sepal much longer then the petals. Dorsal sepal ovate-lanceolate in outline when flattened, 43–48 × 14–16 mm, expanded near the base then tapered to the long-acuminate or attenuate apex. Lateral sepals obliquely erect to erect, hardly embracing the galea, leaving a very wide lateral gap to the petal margins, much of the labellum visible through this gap; upper part of sinus flat when viewed from the side, with a deep, relatively wide central notch when viewed from the front; internally the sinus projecting inwards as a small platform-like projection; conjoined part 14–16 × 8–10 mm, prominently scabrid, narrowed to 2.5 mm wide at base, tapered into the free points; free points 24–27 mm long, involute, tapered, erect, the tips extending above the galea. Petals obliquely linear-lanceolate, 30–33 × 3–4 mm, strongly falcate, long-acuminate, green with white stripes, red-brown toward the apex. Labellum erect, curved forwards in the distal third, the apex protruding prominently through the sinus in the set position; labellum hinge ligulate, 3 × 2 mm; lamina oblong-lanceolate, 15.0–18.0 × 3.2–3.5 mm, red-brown; apex subobtuse to acute; callus raised, 0.7 mm wide near apex; basal appendage 3.0–3.5 mm long, penicillate. Column 14–16 mm long, bent away from the ovary at 35 degrees at the base then erect, green and white; column foot 4 mm long. Column wings 6–7 mm long; basal lobe 3 × 1 mm, at an angle of about 35 degrees; apex obtuse; inner margins incurved, sparsely and shortly ciliate; mid-section 3 mm long, green; apical lobe 1.3 mm long, linear,obtuse. Stigma narrowly scutiform 3–4 × 2 mm, medial on the column, raised. Anther 1.8 mm long, very shortly rostrate. Pollinia linear-falcate, 1.5–1.8 mm long, yellow, mealy.
Similar taxa
Easily recognised by the larger, somewhat narrow flowers with reddish suffusions in the galea and lateral sepals; obliquely erect to erect galea; erect to obliquely erect lateral sepals held well away from the galea so leaving a wide gap between the margins of the galea and the petals, and by the extremely sensitive, oblong-lacneolate, reddish-brown labellum.
Distribution
Endemic. New Zealand: North Island (Waimarino River Plain near Erua and near Cape Palliser), South Island (mainly in the north-west as far south as the Buller River, and also down the Wairau River; exact distribution still unclear). Easily overlooked on account of its short flowering season.
Habitat
Montane (mostly above 600 m a.s.l.). Although exact habitat preferences are uncertain this species seems to prefer damp, shaded, or well-lighted situations in tall forest along river flats, or in steep hill country overlying primarily base-rich geologies (especially calcareous mud and siltstones, limestone, marble and soils derived from andesitic tephra).
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.
Please note, threat classifications are often suggested by authors when publications fall between NZTCS assessment periods – these interim threat classification statuses has not been assessed by the NZTCS panel.
- 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 | Threatened – Nationally Vulnerable | Qualifiers: Sp, DPR, DPS, DPT, EF
Detailed taxonomy
Family
Orchidaceae
Synonyms
None (first described in 1997)
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Ecology
Flowering
November–December
Fruiting
January
Propagation technique
Difficult—should not be removed from the wild.
Other information
Plant of the Month
This plant has been featured as a Plant of the Month – see Trilepidea: NZPCN newsletter for December 2022 for the full story.
Etymology
pterostylis: Winged column
Manaaki Whenua Online Interactive Key
NVS code
The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.
PTEIRW
Previous conservation statuses
2017 | Threatened – Nationally Endangered | Qualifiers: DP, EF, Sp
2012 | Threatened – Nationally Vulnerable | Qualifiers: DP, EF, Sp
2009 | Threatened – Nationally Endangered | Qualifiers: DP, EF, Sp
2004 | Data Deficient
Referencing and citations
References and further reading
de Lange PJ, Heenan PB, Norton DA, Rolfe JR, Sawyer JWD. 2010. Threatened Plants of New Zealand. Canterbury University Press, Christchurch. 471 p.
Jones DL, Molloy BPJ, Clements MA. 1997. Six new species of Pterostylis R.Br. (Orchidaceae) from New Zealand. The Orchadian 12: 266–281. https://www.biodiversitylibrary.org/page/62046409#page/270/mode/1up.
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 irwinii Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/pterostylis-irwinii/ (Date website was queried)