Potamogeton alpinus; the Red Pondweed is a common pondweed on Iceland. This plant grows submerged in ponds and lakes. On Iceland there are a few more Potageton species growing in ponds, lakes, waterways. They can be differentiated by their leaf-shapes. One has to take into account that submerged leaves and floating leaves can differ. The following table describes the leaf shapes of Icelandic Potamogeton species and closely related species of the pondweed family:
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Species name
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Submerged leaf-shape
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Floating leaf-shape
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Status
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P. gramineus
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sessile, sharply pointed top rather narrow
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Broader with long leaf stalks. Also pointed leaf apexes
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In ponds and lakes all around Iceland
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P alpinus
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leaves tapering to the base with obtuse apex's
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usually absent,
if present similar to P. gramineus |
Common
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P. natans
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absent
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rather broad elliptic shaped. Also pointed leaf apexes
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Rather rare
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P. perfoliatus
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Sessile short/broad leaves
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Absent
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Rather rare: prefers relative warmer conditons
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P. praelongus
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Long sessile leaves. Not tapering to the base, almost clasping stems
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absent
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Rather rare
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P. berchtoldii
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Linear leaves
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absent
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Not uncommon
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Stuckenia filiformis
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Thread-shaped leaves
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absent
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Differs from Potamogeton species in having a serie of flower bundles along the flowering stems.
Common, also in interior highland ponds
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Zanichellia palustris
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short gras-like thread-shaped leaves
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absent
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Inflorescences in leaf-axils composed of just one male eand female flower.
Rare
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Ruppia maritima
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Thread-like
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absent
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brackish and saline conditions. Individual flowers long-stalked. These stalks spirally coil at fruiting stage.
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Alas I do not have pictures yest of all Potamogetonaceae (pondweed family) members.
Potamogeton_alpinus / red pondweed is a member of the pondweed family (Potamogetonaceae). The Icelandic name of the Alternate Water-milfoil is Fjallnykra.