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  4. Stuckenia pectinata

Stuckenia pectinata

Close up of fennel-leaved pondweed.<br>Photographer: Rohan Wells, Licence: All rights reserved.
Fennel-leaved pondweed.<br>Photographer: Rohan Wells, Licence: All rights reserved.
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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

Jump to previous conservation statuses

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

Potamogetonaceae

Authority

Stuckenia pectinata (L.) Börner

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

Jump to current conservation status

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)

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