OregonFlora: Potamogeton foliosus vs. Potamogeton subsibiricus

	Potamogeton foliosus	Potamogeton subsibiricus
	leafy pondweed
Stems	flattened, 4–75 cm; nodal glands rarely present.
Leaves	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).
Inflorescences	emersed; spikes continuous (rarely interrupted), 1.5–7 mm; peduncles axillary, recurved, 3–11(37) mm.
Fruits	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 foliosus	Potamogeton subsibiricus
Distribution	[WildflowerSearch map] [BONAP county map]	[BONAP county map]
Discussion	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 498 Nick Otting, Richard Brainerd, Barbara Wilson
Sibling taxa	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	P. alpinus, 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
Synonyms	Potamogeton foliosus ssp. foliosus, Potamogeton foliosus var. foliosus, Potamogeton foliosus var. macellus
Web links	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local Web sites: Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Potamogeton subsibiricus

leafy pondweed

Stems

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

Leaves

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).

Inflorescences

emersed;

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

peduncles axillary, recurved, 3–11(37) mm.

Fruits

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 subsibiricus

Distribution

[WildflowerSearch map]

[BONAP county map]

Discussion

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 498
Nick Otting, Richard Brainerd, Barbara Wilson

Sibling taxa