Potamogeton foliosus
 
Leafy Pondweed

Upper Portion of Shoot

Red Deer River at Hudson Bay
03-August-2021

Note the spikes (indicated by red arrows) terminating short peduncles.

Foliosus: Answers to key questions in Rushes, Bulrushes & Pondweeds plus the remaining Monocots of Saskatchewan, Fascicle 6, Flora of Saskatchewan by Anna Leighton leading to this species. 

Stipular sheaths free from leaf blades; leaves not conspicuously 2-ranked; leaf blade width various; inflorescences unbranched; NOT [Stipular sheaths fused to leaf blades for about half the sheath length, the tips projecting as ligules; leaves stiffly and conspicuously 2-ranked; leaf blades linear to lanceolate; inflorescences often branched]

Leaf margins entire; beaks <= 1 mm long; turions soft or firm; NOT [Leaf margins serrate; beaks 2-3 mm long; turions firm]

Leaf blades linear (i.e. with sides parallel), 0.1-10 mm wide; NOT [Leaf blades ranging from linear-lanceolate to lanceolate, elliptic and ovate, 3-58 mm wide]

Leaf blades to 5 mm wide, lacunae absent or in less prominent bands; rhizomes absent; turions usually present; NOT [Leaf blades 1-10 mm wide; lacunae forming a conspicuous wideband on each side of midrib; rhizomes present; turions absent]

Leaf blades 1-7 (9)-veined, <= 3.5 mm wide, <= 8.2 cm long, slightly tapering at base; stems terete to compressed but not conspicuously compressed and winged; stipular sheaths often inconspicuous, 2-22 mm long; spikes 1.5-16 mm long; fruit 1.5-3.6 mm long; turions soft; NOT [Leaf blades 15-35-veined, 2-5 mm wide, 10-20 cm long, rounded at base; stem conspicuously compressed, winged, almost as wide as the leaves; stipular sheaths conspicuous, 15-35 mm long; spikes 15-30 mm long; fruit 4-5 mm long; turions firm]

Nodal glands absent (present only rarely); peduncles 3-11 (37) mm long, clavate; spikes 1.5-7 mm long; fruit keeled abaxially, the keel undulate;  NOT [Nodal glands usually present on at least some nodes, if absent, then peduncles generally longer than 10 mm and up to 60 mm and fruit not keeled; peduncles cylindrical, filiform or slightly clavate; spikes 1.5-16 mm long; fruit if keeled, the keel not undulate]

 

Potamogeton: Answers to key questions in Rushes, Bulrushes & Pondweeds plus the remaining Monocots of Saskatchewan, Fascicle 6, Flora of Saskatchewan by Anna Leighton leading to this genus. 
Stipular sheaths of submersed leaves usually free from base of leaf, or if fused to leaf, then fused for less than half of the length of the sheath and leaf blades >= 3 mm wide; floating leaves present in some  species; blades of submersed leaves translucent, flattened, not channeled;  peduncles stiff and if long enough then projecting inflorescences above the water surface; NOT [Stipular sheaths of submersed leaves fused to base of leaf for two-thirds or more of the length of the sheath and leaf blades < 3 mm wide; floating leaves absent in all species; blades of submersed leaves opaque, channeled, turgid; peduncles flexible and not projecting inflorescences above the water surface]

 

Potamogetonaceae: Answers to key questions in Rushes, Bulrushes & Pondweeds plus the remaining Monocots of Saskatchewan, Fascicle 6, Flora of Saskatchewan by Anna Leighton leading to this family

Plants larger and with well-defined stems and/or leave; NOT [Plants free-floating aquatics growing on the surface or suspended in water, solitary and 0.5-15 mm across or attached together in larger colonies; identifiable stems and leaves absent]

Plants growing in water (aquatic) with stems, leaves and inflorescences growing underwater (submersed) or floating on the surface, sometimes with inflorescences somewhat elevated above the water (emergent); all leaves cauline, none basal; NOT [Plants growing on land (terrestrial) or in wetlands (paludal) with upper parts of stems, leaves and inflorescences growing well above the water surface (emergent), or if plants aquatic and submersed, then all or at least some leaves basal]

Flowers and fruit not as below, either female flowers solitary in leaf axils have solitary fruit, or the flowers are perfect and 2-many in terminal or axillary spikes; blades various; NOT [Female flowers solitary in leaf axils with 4-5, short-stalked, beaked fruit with dentate convex margins; leaf blades linear, 0.2-1 mm wide, 3.5-4.2 cm long]

Flowers 2 or more in terminal or axillary spikes; leaves submersed or floating, sessile or petiolate, often > 3 cm long, usually alternate with the pair under inflorescences nearly opposite; stipules forming sheaths enveloping stems, but often breaking down with age; NOT [Flowers and fruit solitary in leaf axils at stem nodes; leaves submersed, sessile, 0.5-3 cm long, opposite or whorled; stipules absent]

Fruit sessile on spikes at maturity; spikes several- to many-flowered, exserted beyond sheathing leaf bases at anthesis; peduncles not coiling at base; pistils without stipes; tepals 4, attached to stamens; stipular sheaths usually unattached to leaf bases, if fused, then the free tips (ligules) 2-20 mm long (absent or obscure in Stuckenia vaginata);  floating leaves present in some species; NOT [Fruit borne on stipes up to 35 mm long in umbellate clusters at the tip of peduncles at maturity; spikes 2-flowered, enclosed within inflated leaf sheaths at anthesis; peduncles in some species coiling basally after fertilization; pistils stipitate, perianth absent; stipular sheaths fused to leaf bases for their full length with free tips (ligules) minute or lacking; floating leaves absent]