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northern pondweed, reddish pondweed

variable pondweed

Stems

terete; to 200 cm; nodal glands absent.

terete to flattened; to 150 cm; nodal glands absent.

Leaves

submersed and floating or submersed only.

submersed and floating or submersed only.

Floating leaves

elliptic or oblanceolate to obovate or oblonglinear, 40–70(100) × 10–25(40)mm; reddish green;

base gradually tapering to petiole;

tip obtuse or acute;

veins (7)9–13(15);

petioles 0–12 mm.

elliptic to ovate, 35–40 × 16–20 mm, yellow-green to dark green;

base rounded;

tip acuminate;

veins 11–13;

petioles 30–45 mm.

Submersed leaves

sessile, attached to stem nodes, not attached to stipules;

stipules (12)15–25(40)mm;

tip blunt;

blades oblong-linear to linear-lanceolate, 45–180(250) × 5–20 mm;

base rounded to cuneate;

margins entire;

tip obtuse or acute; lacunae in 0–6 rows on each side of midvein;

veins 7–9.

sessile or rarely petiolate, attached to stem nodes, not attached to stipules;

stipules 10– 16 mm;

tip acute to obtuse;

blades linear to narrowly lanceolate or oblanceolate, 31–91 × 3–27 mm;

base attenuate;

margins entire, rarely wavy;

tip acuminate; lacunae in 1–2 rows on each side of midvein;

veins 3–7(9);

petioles to 30 mm.

Inflorescences

emersed;

spikes cylindric, 10–35 mm;

peduncles terminal or axillary; erect, 30– 100(160)mm.

emersed;

spikes cylindric, 15–35 mm;

peduncles axillary and terminal; erect to ascending, cylindric, 32–77 mm.

Fruits

pedicellate, obovoid; turgid; (2.5)3–3.5 × (1.7)2–2.4 mm, dorsally keeled, laterally keeled or not;

beaks dorsally curved, 0.5–0.9 mm.

sessile; ovoid, laterally compressed, 1.9–2.3 × 1.8–2 mm; greenish brown, dorsally and laterally keeled;

beaks erect, 0.3–0.5 mm.

Potamogeton alpinus

Potamogeton gramineus

Distribution
[WildflowerSearch map]
[BONAP county map]
[WildflowerSearch map]
[BONAP county map]
Discussion

Ponds, lakes, and slow-moving streams. 1200–2200m. BR, BW, Casc. CA, ID, NV, WA; north to British Columbia, east to Greenland; Eurasia. Native.

Potamogeton alpinus is often red when fresh. This species hybridizes with P. nodosus, P. gramineus, and P. praelongus.

Ponds, lakes and streams. 50–2300m. BR, BW, Casc, ECas, Est, WV. CA, ID, NV, WA; north to Northwest Territories, east to Newfoundland, southeast to AZ; Eurasia. Native.

This species hybridizes with P. alpinus, P. illinoensis, P. natans, P. nodosus, P. praelongus, and P. richardsonii.

Source Flora of Oregon, volume 1, page 496
Nick Otting, Richard Brainerd, Barbara Wilson
Flora of Oregon, volume 1, page 498
Nick Otting, Richard Brainerd, Barbara Wilson
Sibling taxa
P. amplifolius, P. berchtoldii, P. crispus, P. diversifolius, P. epihydrus, P. fibrillosus, P. foliosus, P. gramineus, P. illinoensis, P. natans, P. nodosus, P. praelongus, P. pusillus, P. richardsonii, P. robbinsii, P. zosteriformis
P. alpinus, P. amplifolius, P. berchtoldii, P. crispus, P. diversifolius, P. epihydrus, P. fibrillosus, P. foliosus, P. illinoensis, P. natans, P. nodosus, P. praelongus, P. pusillus, P. richardsonii, P. robbinsii, P. zosteriformis
Synonyms Potamogeton alpinus ssp. tenuifolius, Potamogeton alpinus var. subellipticus, Potamogeton alpinus var. tenuifolius Potamogeton gramineus var. gramineus, Potamogeton gramineus var. maximus, Potamogeton gramineus var. myriophyllus, Potamogeton heterophyllus
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