Eryngium undulatum
Past favourite plant finalist
Common names
sea holly
Biostatus
Native – Endemic taxon
Category
Vascular
Structural class
Herbs - Dicotyledons other than Composites
Simplified description
Prostrate, stoloniferous / rhizomatous plant of mostly coastal areas forming grey-green to grey patches in low turf. Summer leaves lanceolate to ovate, margins prickly and undulating. Flowers in umbels on short stems, subtending bracts grey, flowers white.
Flower colours
White
Detailed description
Tufted perennial, with stolons or rhizomes, forming patches up to c. 30 cm in diameter. Basal leaves of 2 forms: winter leaves entire, fistular, septate; summer leaves lanceolate to ovate or spathulate, long-petiolate, deeply spinose-serrate and often undulate, c. 5–12 cm long; non-rosette leaves similar but reduced. Capitula solitary on short peduncles lateral to stolons or arising from rosette, 5–10 mm diam.; involucral bracts 6–9, triangular, mostly 5–7 mm long; bracteoles similar to bracts but smaller. Flowers many (±15–20), white, 1–3 mm diam.; calyx teeth c. 1 mm long. Fruits comprising the two mericarps, each up to 3 mm long, scaly; scales <0.5 mm long with blunt tips.
Similar taxa
The Australian endemic Eryngium vesiculosum is superficially similar but is a taller suberect to erect rather than prostrate plant, with blue rather than glaucous or grey-green involucral bracts that are 4–8.5 mm long rather than 10–16 mm long, and mericarps that are longer (4 mm c.f. 2(-3) mm long).
Distribution
Endemic. New Zealand: North Island (Manawatu and eastern Wairarapa coastline south), South Island (mainly east of the main divide).
Habitat
Mostly coastal. Growing on sandy beaches, coastal gravels, lower drainage areas of rivers, and exposed headlands. Occasionally inland in similar habitats.
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: Sp, CI, DPS, DPT, RR, SO
Detailed taxonomy
Family
Synonyms
New Zealand plants had long been refereed to the Australian endemic Eryngium vesiculosum.
Taxonomic notes
It has long been appreciated that New Zealand plants may be an unnamed, endemic species. Recently Michael & Wilson (2025) examined the relationship between Australian Eryngium vesiculosum and New Zealand plants and concluded that they were different speciesd. The New Zealand plant they considered as a new unnamed endemic which they described as E. undulatum (Michael & Wilson 2025).
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Ecology
Life cycle and dispersal
Spiny mericarps are dispersed by attachment and wind (Thorsen et al., 2009).
Wetland plant indicator status rating
Information derived from the revised national wetland plant list prepared to assist councils in delineating and monitoring wetlands (Clarkson et al., 2021 Manaaki Whenua – Landcare Research Contract Report LC3975 for Hawke’s Bay Regional Council). The national plant list categorises plants by the extent to which they are found in wetlands and not ‘drylands’. The indicator status ratings are OBL (obligate wetland), FACW (facultative wetland), FAC (facultative), FACU (facultative upland), and UPL (obligate upland). If you have suggestions for the Wetland Indicator Status Rating, please contact: [Enable JavaScript to view protected content]
FAC: Facultative
Commonly occurs as either a hydrophyte or non-hydrophyte (non-wetlands).
Other information
Plant of the Month
This plant has been featured as a Plant of the Month – see Trilepidea: NZPCN newsletter for April 2010 for the full story.
Etymology
eryngium: From the Greek eryngion, a type of spiny-leaved thistle resembling sea holly
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.
ERYVES
Chromosome number
2n = 64
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 | Threatened – Nationally Vulnerable | Qualifiers: DP, RR, SO, Sp
2012 | At Risk – Declining | Qualifiers: DP, SO, Sp
2009 | At Risk – Declining | Qualifiers: DP, SO, Sp
2004 | Gradual Decline
Regional conservation statuses
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 “Regional conservation status of indigenous vascular plants in Otago” Jarvie S et al. (2024) report.
Otago: 2024 | Threatened – Regionally Critical | Qualifiers: CI, NR, OL
Referencing and citations
References and further reading
Michael, P.W.; Wilson, P.G. 2025: Eryngium undulatum, a new name for the New Zealand plant long known as E. vesiculosum. Telopea 29: 83–89. https://doi.org/10.7751/telopea20306
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. https://doi.org/10.1016/j.ppees.2009.06.001.
Attribution
Description from Michael & Wilson (2025).
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Eryngium undulatum Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/eryngium-undulatum/ (Date website was queried)