Acianthus rivularis A.Cunn., Corysanthes rivularis (Hook.f.) Hook.f., Nematoceras rivulare (A.Cunn.) Hook.f.
Vascular – Native
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.
Current conservation status
The threat classification status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2017 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website This report includes a statistical summary and brief notes on changes since 2012 and replaces all previous NZTCS lists for vascular plants. Authors: By Peter J. de Lange, Jeremy R. Rolfe, John W. Barkla, Shannel P. Courtney, Paul D. Champion, Leon R. Perrie, Sarah M. Beadel, Kerry A. Ford, Ilse Breitwieser, Ines Schönberger, Rowan Hindmarsh-Walls, Peter B. Heenan and Kate Ladley. Please note, threat classifications are often suggested by authors when publications fall between NZTCS assessment periods – a suggested threat classification status has not been assessed by the NZTCS panel.
2018 | At Risk – Naturally Uncommon
Previous conservation statuses
2017 | At Risk – Naturally Uncommon | Qualifiers: DP, RR, Sp, St
2012 | Data Deficient
2009 | Data Deficient
2004 | Data Deficient
Endemic. North Island. Northland and Taranaki probably elsewhere.
Lowland. Confined to wet, shaded sites within tall indigenous forest. Usually found along stream sides (often within moss on stones and rocks within the stream bed), but also on seepages on cliff faces and within damp, mossy, dripping holes on talus slopes
Colonial, terrestrial, tuberous, glabrous, late winter to summer-green herb. Tuberoids globose to ellipsoid on extended roots. Plant at flowering to 40 mm tall. Leaf solitary (rarely paired), fleshy, subsessile or with a short petiole 5-10 mm long; lamina 20-30 x 15-25 mm long, oval to orbicular, apiculate, rounded to cordate at base; dark green to yellow green, margins and sometimes whole of upper surface flecked with purple or red, underside silvery pellucid. Flower erect, mostly large for plant, (15)-20(-25) mm long, held well above leaf, mostly dark crimson black; peduncle short and stout, 2.5-3.5 mm long. Ovary 8.5-10.0 mm long, narrowly oblong to ellipsoid, yellow-green, erect or slightly curving forward over leaf; subtended by two unequal floral bracts, the smaller projecting toward leaf, 1.5-2.0 mm long, linear-subulate to lanceolate-subulate, terete, pale green to cream, spotted or flecked with crimson, the larger smaller than, equal to or exceeding the ovary, (2.5-)8.8(-11.0) mm long, lanceolate to linear-lanceolate, curved, deeply keeled and mostly closely sheathing ovary for about one third to half of length, apex acute, green, usually with purple or reddish striae or flecks. Dorsal sepal membranous, more or less equal to labellum length 15-20 mm long, greenish with purple-red crimson-black striate or flecks, lanceolate-acuminate, apex acute, erect then arched forwards, or downwards, very rarely upwards. Lateral sepals and petals subsimilar, 20-30 mm long, filiform, cream to yellow green more or less flecked with red, greatly exceeding the labellum, held well above leaf. Labellum conspicuous, dark crimson-black, auriculate at base,; labellum tube 1.5-3 mm long, erect at first then abruptly deflexed at c. 90 degrees and expanding into a gradually broadening lamina; lamina (15-)20(-25) x (6-)10(-16) mm, narrowly obtuse when flattened, upper margins sharply folded inwards, upper third to half more or less overlapping, lower surface spreading and deeply grooved; apex usually held well above leaf; margins initially entire, becoming erose to finely and irregularly denticulate on either side, and with a short to moderately long down-curved apiculus; apiculus not or only rarely touching leaf.
Manaaki Whenua Online Interactive Key
Corybas rivularis is a very variable and at least four forms occur within it that probably merit formal taxonomic recognition (Irwin 1994, 1996). Corybas rivularis was long confused with C. orbiculatus (e.g., Moore & Edgar 1970).
October - November
November - January
Difficult - should not be removed from the wild.
Probably qualifies for listing as Sparse. Corybas rivularis sens.str. does seem to be genuinely uncommon but not threatened. Other segregates from the species are now well known and are awaiting formal taxonomic recognition. Past uncertainy over the conservation status of C. rivularis was because of past uncertainity over the status of these forms.
corybas: Helmet flower
rivularis: Of streams
Where To Buy
Not commercially available.
Considerable research is underway to investigate the validity of the segregate genera split from Corybas R.Br. by Jones et al. (2002). Whilst much of that work has yet to be published, on advice from Australian Orchidologists Peter Weston and Stephen Hopper (pers. comm., July 2011, November 2014), all of the segregate genera recognised for New Zealand by Jones et al. (2002) are returned to Corybas.
Nematoceras panduratum (Cheeseman) Molloy, D.L.Jones et M.A.Clem. is probably conspecific. It differs by its slightly larger size and pandurate leaf. It is a poorly known species that grows in similar habitats to Corybas rivularis.
Fact Sheet prepared for NZPCN by P.J. de Lange 14 April 2007. Description based on herbarium specimens and herbarium material.
References and further reading
Jones, D.L.; Clements, M.A.; Sharma, I.K.; Mackenzie, A.M.; Molloy, B.P.J. 2002: Nomenclatural notes arising from studies into the Tribe Diurideae (Orchidaceae). The Orchadian 13: 437-468.
Lehnebach, C. 2016: New combinations and a replacement name for three New Zealand spider orchids (Corybas). The New Zealand Native Orchid Journal 139. 4-5.
Lyon, S. P. 2014: Molecular systematics, biogeography, and mycorrhizal associations in the Acianthinae (Orchidaceae), with a focus on the genus Corybas. PhD Thesis, University of Wisconsin-Madison. USA.
Moore, L.B.; Edgar, E. 1970: Flora of New Zealand. Vol. II. Government Printer, Wellington.
St George, I.; Irwin, B.; Hatch, D. 2005: Field guide to the New Zealand Orchids. The New Zealand Native Orchid Group, Wellington, 136pp.
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Corybas rivularis Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/corybas-rivularis/ (Date website was queried)