Page author: Kevin Armitano
Potamogeton obtusifolius
blunt-leaved pondweed

Origin: Native

Conservation Status: Sensitive in Washington (WANHP)


Annual, perennial herb, slender, rhizomes absent; cauline stems slightly compressed, 35-90 cm, without spots; glands yellow-green to gold, 0.2-1 mm diameter; turions terminal, abundant, 3.5-7.8 cm x 2.3--5.1 mm, soft.


Leaves 2-ranked; outer leaves 3-4 per side, base not corrugate, apex apiculate to obtuse; inner leaves undifferentiated; leaves submersed, often spirally arranged, sessile, flaccid; stipules persistent, inconspicuous, convolute, free from blade, not ligulate, white, 0.6-1.8 cm, fibrous, rarely shredding at tip, apex obtuse; blade light green to somewhat reddish, linear, not arcuate, 3-8.2 cm x 1--3.5 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, obtuse or round-apiculate, lacunae in 1-3 rows each side of midrib; veins 3.


Inflorescences panicle of spikes, unbranched, emersed, cylindric; peduncles not dimorphic, axillary, erect, rarely recurved, cylindric, 0.8-1.9(-4.2) cm, may project above water surface; spike not dimorphic, cylindric, 8-13 mm; pistils 1 or 4


Fruits sessile, olive-green to brown, obovoid, turgid, abaxially keeled or not, laterally keeled or not, 2.5--3.6 x 1.7--2.4 mm, lateral keels without points; beak erect, 0.8-1 mm; sides without basal tubercles; embryo with 1 full spiral.

Accepted Name:
Potamogeton obtusifolius Mertens & W.D.J. Koch
Publication: Deutschl. Fl., ed. 3. 1: 855. 1823. 1823.

Synonyms & Misapplications:
(none provided)
Additional Resources:

PNW Herbaria: Specimen records of Potamogeton obtusifolius in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Potamogeton obtusifolius checklist entry.

E-Flora BC: Potamogeton obtusifolius atlas page.

CalPhotos: Potamogeton obtusifolius photos.

USDA Plants: Potamogeton obtusifolius information.

3 photographs:
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