Stuckenia pectinata
Common names
fennel-leaved pondweed, sago pondweed
Biostatus
Native
Category
Vascular
Structural class
Herbs - Monocots
Detailed description
Aquatic rhizomatous herb. Rhizomes forming extensive networks in soft sediment, forming swollen bulb-like buds in autumn. Branches numerous, slender, delicate (rather brittle), 0.1-3 m or more long. Stipulate, with stipules fused to leaf base, forming a sheathing ligulate stem for 10-40 mm, the free portion (ligule) membraneous, 5 mm long. Leaves all submersed, 50-120 x 1 mm, dark green to brown-green, entire, narrow-linear (with transverse veins visible), tapering to an acute, membraneous tip. Peduncles slender, of varying length. Inflorescence a discontinuous brown spike 20-40 mm, with the lower flower clusters (whorls) well separated. Fruit, an achene 3 x 2.5 mm, light pinkish brown, turgid and rounded, without keel or beak.
Similar taxa
Most likely to be confused with Ruppia spp. with which it often grows and from whose species it can be distinguished by the ligulate acute-tipped leaves, tuberous stems, and spicate inflorescences.
Distribution
Indigenous to New Zealand where it has been collected from the North, South and Chatham Islands. A cosmopolitan species known from throughout the world. No critical study on its worldwide variation seems to have been done.
Habitat
Usually in brackish water, such as in slow moving tidal streams or lagoons, but also found in shallow lowland pools.
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: SO
Threats
Probably more overlooked than actually threatened. Nevertheless there is some evidence that this species has declined for sites where it was formerly common over the least 20 or so years, and it remains absent from large stretches of apparently suitable habitat where it was once known 100 or more years ago. The main threat seems to be wetland modification and or drainage, particularly of those brackish wetland systems, or where streams and rivers enter the sea. However, the species can survive some modification and has even been collected in recently established channels, and within pools of water on the floor of gravel quarrys. Thus this species may prove to be naturally uncommon rather than genuinely declining. Further field survey is needed to clarify its exact status.
Detailed taxonomy
Family
Synonyms
Potamogeton pectinatus L., Coleogeton pectinatus (L.) D.H.Les et R.R.Haynes comb. inval.
Taxonomic notes
The genus Stuckenia was erected in 1912. It differs from Potamogeton by the long stipular sheaths, tubular leaves with air channels bordering the midrib, flexuous peduncles, hydrophilous pollination and a hexaploid chromosome number (x = 13). Submerged leaves of Stuckenia are characteristically opaque and somewhat turgid. Stuckenia is further segregated from Potamogeton and Groenlandia by the fact that it never forms hybrids with either. Stuckenia pectinata is known to have aneuploids but the one New Zealand count known is not aneuploid and is typical of the species.
Endemic taxon
No
Endemic genus
No
Endemic family
No
Ecology
Flowering
January - February
Fruiting
January - March
Propagation technique
Difficult and should not be removed from the wild.
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]
OBL: Obligate Wetland
Almost always is a hydrophyte, rarely in uplands (non-wetlands).
Other information
Etymology
pectinata: Comb-bearing
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.
STUPEC
Chromosome number
2n = 78
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: SO, Sp
2012 | At Risk – Naturally Uncommon | Qualifiers: PD, SO, Sp
2009 | At Risk – Naturally Uncommon | Qualifiers: DP
2004 | Sparse
Regional conservation statuses
Otago: 2024 | Threatened – Regionally Vulnerable | Qualifiers: DPR, DPS, DPT, NR, OL, RR
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.
Auckland: 2025 | Regionally Data Deficient | Qualifiers: SO
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
Moore LB, Edgar E. 1970. Flora of New Zealand, Volume II. Indigenous Tracheophyta: Monocotyledones except Gramineae. Government Printer, Wellington, NZ. 354 p.
Attribution
Fact sheet prepared for NZPCN by P.J. de Lange (January 2006). Description adapted from Moore & Edgar (1970)
Some of this factsheet information is derived from Flora of New Zealand Online and is used under a Creative Commons Attribution 3.0 New Zealand licence.
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Stuckenia pectinata Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/stuckenia-pectinata/ (Date website was queried)