West Highland Flora

Perfoliate Pondweed


Potamogeton perfoliatus

 

Potamogeton perfoliatus

Photo Carl Farmer
30 Sep 2003 Storr Lochs, Skye

Quite frequent in lochs

Leaves c 2-6 cm long.

ID: Leaves almost completely encircle stem with rounded lobes, see bottom right pic (not all will circle it as completely as in that pic)

Other features: Stems round in cross-section, without grooves.  All leaves submerged (except when exposed by falling water level), no specialised floating leaves.  Usually occurs in deep water away from the loch edge, and so mostly found in the form of bits broken off and washed up, as in these pictures.  Stipules very flimsy, no more than 2 cm long, disappearing early in the season.

Leaves are narrower in situations lacking light and calcium, and broader in places rich in these elements.  The ones in these pictures are rather narrow as would be expected from a non-alkaline loch.  I have photos of even narrower ones from a different loch but can't rule out a hybrid in their case so am not displaying them.

The fruits are densely arranged on a typical pondweed spike (see e.g. Bog Pondweed).  Unlike some pondweeds, the stalk is not thickened upwards towards the base of the spike.

 

Potamogeton perfoliatus

Photo Carl Farmer
30 Sep 2003 Storr Lochs, Skye

  Potamogeton perfoliatus

Photo Carl Farmer
30 Sep 2003 Storr Lochs, Skye
 

  Left: washed up stem on loch shore.

Above: leaf-base with stem cut across to show how leaf encircles stem.


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