Cyperus insularis
Biostatus
Native – Endemic taxon
Category
Vascular
Structural class
Sedges
Detailed description
Robust sedge up to 2 m tall with leaves crowded at base of culms. Culms stout, triquetrous, glabrous, striated, green, rarely brown in distal part, at base, upright at flowering, collapsing at seed fall. Leaves 1.4–3.2 mm × 1–2 m, grey green, strongly keeled, leaf margin and keel sharply scabrid, sheath light pink to light purple-pink. Inflorescence a terminal umbel of 6–12 unequal rays, each subtended by a leaf-like involucral bract, these 0.3–3.2 mm × 0.1–1.15 m, grey-green, base green, often flushed light pink to purple-pink, or rarely pale brown. Spikelets 9–12 mm long. Glumes 3–5.8 × 2–2.8 mm, ovate-oblong or ovate, green some times pale green or translucent, distal end and margin red-brown, drying yellow-brown to light brown, keeled, mcuronate or obtuse, crowded into a dense spike 40–60 mm long. Stamens with persistent filaments. Nut 1.6–1.7 mm, red-brown to orange-brown, oblong to broadly oblong.
Similar taxa
Distinguished from C. ustulatus A.Rich. by the grey-green leaves and involucral bracts, leaf sheaths light pink to purple-pink the culm/involucral bract junction green, pink or rarely pale brown, by the stout, usually branched rays, and by the culms which collapse after flowering. There are other floral characters which also distinguish these species, for these and other details see Heenan & de Lange (N.Z.J.Bot. 43: 351–359 (2005) - see link below).
Distribution
Endemic. Known only from the Kermadec, Three Kings Islands, and northern North Island and associated offshore islands south to Port Waikato and Moutohoura (Whale) Island (Bay of Plenty).
Habitat
Northern offshore islands, and rocky headlands, usually in association with sea bird nesting grounds, though on the Kermadec Islands, where it is the only species present it is also present along sandy beaches and in swamps.
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 – Declining | Qualifiers: DPR, DPS, DPT, PD, RR
Threats
Declines are happening on Raoul and Macauley Islands, and there is some evidence of this also in the North Island part of its range. The nature of the decline is not clear, though in some places, such as Macauley Island it appears to be part of natural succession while on Raoul the decline at Denham Bay may be due to the spread of buffalo grass (Stenotaphrum secundatum). Within the mainland portion of its North Island range, the species appears restricted to sites frequented by sea birds, especially their nesting grounds, and it seems that as these habitats have been lost, so too has the Cyperus.
Detailed taxonomy
Genus
Family
Synonyms
None - this species is a recently recognised segregate of the New Zealand endemic C. ustulatus A.Rich
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Ecology
Flowering
July–December
Fruiting
July–April
Life cycle and dispersal
Nuts are dispersed by water, granivory and attachment (Thorsen et al., 2009).
Propagation technique
Easily grown from fresh seed, and often self sows in gardens. A quite attractive plant which may in time prove popular in cultivation. However it should be planted with caution, the leaf, keel and culm margins are very sharp and can cause very deep cuts.
Other information
Etymology
cyperus: From the ancient Greek name for sedge, kypeiros
insularis: From the Latin insula ‘island, pertaining to or growing on islands
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.
CYPINS
Chromosome number
2n = 112-114
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 – Declining | Qualifiers: PD, RR
2012 | At Risk – Declining | Qualifiers: RR
2009 | At Risk – Declining
2004 | Not Threatened
Regional conservation statuses
Auckland: 2025 | Regionally Threatened – Regionally Endangered | Qualifiers: DPR, DPS, DPT, PF, RR
The regional threat classification system leverages off the national assessments in the NZTCS, providing information relevant for the regional context. Auckland conservation status information is sourced from the “Conservation status of vascular plant species in Tāmaki Makaurau / Auckland” Simpkins E et al. (2025) report.
Referencing and citations
References and further reading
Heenan PB, de Lange PJ. 2005. Cyperus insularis (Cyperaceae), a new species of sedge from northern New Zealand. New Zealand Journal of Botany 43: 351–359. https://doi.org/10.1080/0028825X.2005.9512958.
Thorsen MJ, Dickinson KJM, Seddon PJ. 2009. Seed dispersal systems in the New Zealand flora. Perspectives in Plant Ecology, Evolution and Systematics 11: 285–309.
Attribution
Fact Sheet prepared for NZPCN by P.J. de Lange (31 July 2004). Description adapted from Heenan & de Lange (2005).
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Cyperus insularis Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/cyperus-insularis/ (Date website was queried)