The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links

northern pondweed, reddish pondweed

leafy pondweed

Stems

terete; to 200 cm; nodal glands absent.

flattened, 4–75 cm; nodal glands rarely present.

Leaves

submersed and floating or submersed only.

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

stipules 2–22 mm; greenish to brown, membranous to slightly fibrous;

veins not persisting;

blades linear, 13–82 × 0.3–2.3 mm;

margins entire;

tip acute to apiculate; lacunae rarely present;

veins 1–3(5).

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.

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.

Inflorescences

emersed;

spikes cylindric, 10–35 mm;

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

emersed;

spikes continuous (rarely interrupted), 1.5–7 mm;

peduncles axillary, recurved, 3–11(37) 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; round to obovoid, flattened, 1.5–2.7 × 1.2–2.2 mm; olivegreen to green-brown, dorsally and laterally keeled;

beaks erect, 0.2–0.6 mm.

Potamogeton alpinus

Potamogeton foliosus

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 slow or fast-moving streams. 0–2000 m. BR, BW, Col, ECas, Est, Lava, Owy, Sisk, WV. CA, ID, NV, WA; north to AK, east throughout most of Canada and the US, south to Central America. Native.

Potamogeton foliosus is the most common linear-leaved pondweed in North America. The undulating fruit keel distinguishes this species and P. fibrillosus from our other linear-leaved pondweeds. Immature plants usually cannot be distinguished from P. berchtoldii or P. pusillus.

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. gramineus, 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 foliosus ssp. foliosus, Potamogeton foliosus var. foliosus, Potamogeton foliosus var. macellus
Web links