UW Burke Herbarium species comparison

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Potamogeton foliosus

Potamogeton amplifolius

leafy pondweed

broad-leaved pondweed, large-leaved pondweed
Habit Aquatic, herbaceous perennials from slender rhizomes, the stems freely branching, somewhat compressed and narrow winged, scarcely 1 mm. broad, up to 10 dm. long. Aquatic, herbaceous perennials from slender rhizomes, the terete stems up to 4 mm. thick and 1 m. long, simple or sparingly branched above.
Leaves

Leaves all submersed, without basal glands, narrowly linear, 1-1.5 mm. broad and up to 10 cm. long, acute, 3-nerved, bordered toward the base with air chambers;

stipules united and surrounding the stem, 5-15 mm. long, ultimately disintegrating.

Leaves alternate, the submersed leaves short-petiolate, the upper ones 8-20 cm. long and 2-5 cm. broad, acute at both ends, folded, and sickle-shaped in outline, 25- to 45-nerved; floating leaves with long, stout petioles, the blades leathery, ovate to ovate-elliptic, acute or rounded at the base, 5-10 cm long and 2-4 cm. broad;

stipules to 10 cm. long, free of the petiole.
Flowers

Inflorescence of spikes up to 5 mm. long with 2-3 whorls of crowded, sessile flowers;

peduncles stout, rarely over 2 cm. long;

perianth of 4 clawed segments, each with an upturned, oval blade;

stamens 4, fused with the claws;

pistils 4, sessile.

Flowers perfect, in densely-flowered spikes on peduncles 7-15 cm. long;

perianth of 4 clawed segments, each with an upturned, oval blade;

stamens 4, fused with the claws;

pistils 4, sessile.
Fruits

Achenes obliquely obovoid, 2 mm. long, with a prominent dorsal keel.

Achenes obliquely ovoid, 4-5 mm. long, with a sharp dorsal keel and 2 lateral keels.

Potamogeton foliosus

Potamogeton amplifolius
Flowering time June-August June-August
Habitat Standing to moving, shallow water. Lakes and ponds, tolerant of deep waters.
Distribution
Occurring on both sides of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast.
[WildflowerSearch map]
[BONAP county map]
Occurring on both sides of the Cascades crest in Washington; British Columbia to California, east to the Atlantic Coast.
[WildflowerSearch map]
[BONAP county map]
Origin Native Native
Conservation status Not of concern Not of concern
Sibling taxa
P. alpinus, P. amplifolius, P. berchtoldii, P. crispus, P. epihydrus, P. fibrillosus, P. friesii, P. gramineus, P. illinoensis, P. natans, P. nodosus, P. obtusifolius, P. praelongus, P. pusillus, P. richardsonii, P. robbinsii, P. strictifolius, P. zosteriformis
P. alpinus, P. berchtoldii, P. crispus, P. epihydrus, P. fibrillosus, P. foliosus, P. friesii, P. gramineus, P. illinoensis, P. natans, P. nodosus, P. obtusifolius, P. praelongus, P. pusillus, P. richardsonii, P. robbinsii, P. strictifolius, P. zosteriformis
Web links 
Unless otherwise noted, all data comes from the University of Washington's Burke Herbarium.



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