West Highland Flora

Various-leaved Pondweed


Potamogeton gramineus

 

Potamogeton gramineus

Photo Carl Farmer
24 Aug 2003 Suardal, Skye

This is the only picture I have showing both submerged and floating leaves together, but neither are well shown, being covered with the same kind of debris as the loch floor.

Occasional in lochs

Submerged leaves typically c 3 cm long, can be much longer.

ID: Has submerged leaves (like those in bottom picture), and may also have floating leaves (like those in second picture on page) but the latter may be absent.  Note that submerged leaves could be floating or floating leaves submerged depending on water level.  ID that follows relates to the submerged type of leaf.  These are unstalked, but not at all clasping the stem, at least 5 times as long as wide, and have a short projecting point at the tip.  Together with a round, not flattened or grooved, stem, this should identify the plant.

Other features: Plant typically has many short leafy shoots close together on the loch bed, looking more small-leaved and compact than most pondweeds.  A few of the longer shoots may have floating leaves, which are totally different from the submerged leaves, being opaque, elliptical and long-stalked.

The stipules are stiff, curved so as to fit the stem, but free from it, and very approximately a third as long as the leaf in whose axil they sit.  The submerged leaves have only 2-3 lengthwise veins either side of the midrib; these are fainter than the midrib but equal to each other, or the outermost fainter.

The fruits are densely arranged on a typical pondweed spike (see e.g. Bog Pondweed) but the stalk is thickened upwards towards the base of the spike.

 

 

 

Potamogeton gramineus

Photo Carl Farmer
24 Aug 2003 Suardal, Skye
Middle leaf blade 2.6 cm long

  Potamogeton gramineus

Photo Carl Farmer
24 Aug 2003 Suardal, Skye

  Above: Submerged leaves.

Left: Floating leaves, which have not
quite reached the surface (or possibly
they did once reach the surface and
then the water level rose).

 

 

 

Potamogeton gramineus

Photo Carl Farmer
24 Aug 2003 Suardal, Skye
 

A naturally detached piece floating on loch surface.

 

Potamogeton gramineus

Photo Carl Farmer
24 Aug 2003 Suardal, Skye
 

The same piece on welly boot.  Note how leaf facing to the left has pointed tip and stiff stipule (in angle between leaf and stem)


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