PERFOLIATE PONDWEED

Potamogeton perfoliatus

Pondweed Family [Potamogetonaceae]

month8may month8jun month8june month8jul month8july month8aug month8sep month8sept

status
statusZnative
flower
flower8green
morph
morph8actino
petals
petalsZ4
type
typeZspiked
type
typeZbell
stem
stem8round
sex
sexZbisexual

9th Aug 2018, Rufford Branch, Leeds & L/pool Canal, Lancs. Photo: © RWD
The leaves are said to be submerged with no floating leaves, but this specimen may have been sliced by the propeller of a passing narrowboat, which is maybe how your Author came to notice it in the first place: floating on the surface near the waters edge.


9th Aug 2018, Rufford Branch, Leeds & L/pool Canal, Lancs. Photo: © RWD
The leaves can vary between being broadly ovate (as in this specimen) or narrowish oblong-ovate. Bright-green on the upper surface with noticeable very pale veins but whiter on the under surface (although there may be something in the water making the underside seem white (there are patches of green).


9th Aug 2018, Rufford Branch, Leeds & L/pool Canal, Lancs. Photo: © RWD
The leaves are cordate around the main stem, clasping the stem without stalks about half way around - hence the name perfoliate. Sometimes they may completely clasp the stem almost all the way around. They can vary considerably in size from 20 to 110mm long and being anywhere between 1.3 and 10 times as long as they are wide.


9th Aug 2018, Rufford Branch, Leeds & L/pool Canal, Lancs. Photo: © RWD
The leaves are usually blunt at the tip. The stipules son disappear; none present on these specimens, but before they fall off they are between 2.5 and 22mm long.


9th Aug 2018, Rufford Branch, Leeds & L/pool Canal, Lancs. Photo: © RWD
Leaves blunt at the tip. The veins follow the outline of the leaf, with the veins nearer the centre at ever increasing flattness; the central one is linear without curvature but is wider. There are much fainter veins in the intersticial regions between the veins.

Your Author spotted no fruits on this damaged specimen, but when there they are 2.6 to 3.5mm long.


Not to be semantically confused with : Perfoliate Pepperwort (Lepidium perfoliatum), Perfoliate Honeysuckle (Lonicera caprifolium), Perfoliate Penny-cress (Microthlaspi perfoliatum), Perfoliate Alexanders (Smyrnium perfoliatum) [plants with similar names in differing families]

Hybridizes with :

  • Long-stalked Pondweed (Potamogeton praelongus) to produce Potamogeton × cognatus × which is found in very few locations, the first being in Lincolnshire in 1943.

Some similarities to : Flower ()

Slight resemblance to : American Pondweed (Potamogeton epihydrus) but the floating upper leaves are in opposite pairs on fairly long stalks and have a narrow whitish band across the leaf just beyond the stalk. There lower submerged leaves which are entirely different: long but narrow ribbons which are similarly in opposite pairs up the stem.

Distinguishing Feature : Perfoloiate leaves!

It thrives in mildly acid to neutral water in lakes, canals, ponds and slow moving stream up to a height of 780m, is native and is widespread throughout most of the British Isles.


  Potamogeton perfoliatus  ⇐ Global Aspect ⇒ Potamogetonaceae  

Distribution
 family8Pondweed family8Potamogetonaceae
 BSBI maps
genus8Potamogeton
Potamogeton
(Pondweeds)

PERFOLIATE PONDWEED

Potamogeton perfoliatus

Pondweed Family [Potamogetonaceae]