Potamogeton polygonifolius

Potamogeton polygonifolius
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Monocots
Order:	Alismatales
Family:	Potamogetonaceae
Genus:	Potamogeton
Species:	P. polygonifolius
Binomial name
Potamogeton polygonifolius Pourret

Potamogeton polygonifolius or bog pondweed, is an aquatic plant. It is found in shallow, nutrient-poor, usually acid standing or running water, bogs, fens and occasionally ditches.

Bog pondweed is a perennial, growing from creeping rhizomes. The stems are up to 0.7 m long, terete and unbranched. The submerged leaves are long (60–160 mm) and fairly narrow (2.5–24 mm), delicate and translucent with long (14–80 mm)petioles, tending to decay rather early in the season, typically once the floating leaves appear. The floating leaves are opaque, 40-105 x 15–70 mm, usually brownish or dark green in colour with a pink tint when young, with inconspicuous secondary veins. There are no turions.

The inflorescences are up to 42 mm long and produce numerous small greenish flowers. The fruits are 1.9-2.6 mm x 1.4-1.9 mm, larger than P. coloratus but smaller than P. natans.

Bog pondweed occurs both as terrestrial plants in seeps and wet moss, and as aquatic forms, and is very variable. Terrestrial forms in particular can be very difficult to identify. It is most likely to be confused with P. natans which it resembles in general habit, but can usually be distinguished by the presence of submerged leaves (these are reduced to strap-like phyllodes in P.natans) and the absence of a discoloured mark at the base of the floating leaves. The submerged leaves of P. alpinus can be similar, but these are sessile. Although a common plant, bog pondweed does not seem to hybridise readily with other pondweeds, though hybrids with P. natans (P. × gessnacensis G.Fisch.), P. gramineus, P. alpinus (P. × spathulatus Schrad. ex W.D.J.Koch & Ziz), P. berchtoldii (P. × rivularis Gillot)and P. pusillus have been recorded.

Potamogeton polygonifolius is mainly restricted to western Europe (Britain, Ireland, France, Netherlands, Belgium, Denmark). It is more localised in the rest of its range including Northern Iberia, Germany, mainland Italy, Sicily, southern Scandinavia, the Baltic states, the Balkans and eastern Europe. There are outlying populations in North Africa (Morocco, Algeria), Orkney, Shetland, the Faroes and Newfoundland, and fossils have been found in Russia. The taxonomic status of populations in the Himalayas requires confirmation. A record from China was based on a misidentification of P. distinctus.

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Wikipedia