Potamogeton suboblongus


Potamogeton: river dweller
suboblongus: nearly oblong

Common Name(s)

Mud pondweed

Current Conservation Status

2012 - Not Threatened

Conservation status of New Zealand indigenous vascular plants, 2012
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2012 using the New Zealand Threat Classification System (NZTCS). This report includes a statistical summary and brief notes on changes since 2009 and replaces all previous NZTCS lists for vascular plants. Authors: Peter J. de Lange, Jeremy R. Rolfe, Paul D. Champion, Shannel P. Courtney, Peter B. Heenan, John W. Barkla, Ewen K. Cameron, David A. Norton and Rodney A. Hitchmough. File size: 792KB

Previous Conservation Status

2009 - Not Threatened
2004 - Not Threatened


Potamogeton suboblongus Hagström



Flora Category

Vascular - Native

NVS Species 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.

Structural Class

Monocotyledonous Herbs


Endemic. New Zealand: North, South and Stewart Islands


Coastal to subalpine, being mostly found in upper montane and subalpine areas in the northern part of its range. Potamogeton suboblongus is more commonly found in shallow, muddy hollows in forest, and colonising tarns and alpine soaks and pools which may partially dry out in summer.


Aquatic, submerged or floating, or ± semi-terrestrial on muddy ground and seepages, rhizomatous little-branched, perennial herb. Rhizomes usually buried in firm mud; leafy branches erect, usually simple, long or short, often rooted at leaf-bearing nodes. Stipules c.20–30 mm long, free, open, membranous and often conspicuous. Leaves weakly dimorphic, entire; lower leaves apparently not regularly submersed, similar to upper leaves, being somewhat more narrowly elliptic and with fewer, more obscure nerves than emergent leaves; upper and emergent leaves long- or short-petiolate, lamina 15–60 × 8–35 mm, broad-elliptic, rarely oval, subacute and sometimes shortly attenuate at tip, firm and opaque, longitudinal nerves 11–21 in all, usually several laterals emerging from midrib. Inflorescence a densely flowered spike, 10-20 mm long. Peduncles arising in axils of upper leaves, simple, stout, erect, standing well above leaves. Achenes c.2.0 × 1.5 mm, reddish when ripe, neither flattened nor strongly keeled, beak short but slightly curved.

Similar Taxa

Distinguished from Potamogeton cheesemanii by the scarcely dimorphic foliage (i.e. only slight differences between submersed and emergent leaves), by the near absence of submersed leaves (these if present of similar size and shape to emergent foliage), by the broadly elliptic, subacute floating leaves, which have usually 6 or more nerves on either side of midrib; and by the swollen, reddish, not or only weakly keeled achenes.


December - March


January - April

Propagation Technique

Easily grown from rooted pieces and fresh seed, An attractive plant for a small, shallow pond or damp, shaded hollow. In warmer, lowland areas this species prefers a cool site


Not Threatened

Chromosome No.

2n = 28

Endemic Taxon


Endemic Genus


Endemic Family



Fact sheet prepared for NZPCN by P.J. de Lange (16 February 2012). Description adapted from Moore & Edgar (1970).

References and further reading

Moore, L.B.; Edgar, E. 1970: Flora of New Zealand. Vol. II. Government Printer, Wellington.

This page last updated on 6 Dec 2014