Burke: Potamogeton gramineus vs. Potamogeton vaseyi

	Potamogeton gramineus	Potamogeton vaseyi
	grassy pondweed, variable pondweed
Habit	Aquatic, herbaceous perennials from slender rhizomes, the slender stems freely branching, sub-terete, up to 2 m. long.
Leaves	Leaves alternate, the submersed leaves sessile, linear to lanceolate or oblanceolate, 3-9 cm. long and 3-10 mm. broad, 3- to 7-nerved; floating leaves long-petiolate, elliptic to oblong-elliptic, 2-5 cm. long and 1-2 cm. broad, 13- to 19-nerved; stipules open, firm, up to 3 cm. long.
Flowers	Flowers perfect, in 6-10 crowded whorls, in spikes 1.5-2.5 cm. long on peduncles 4-10 cm. long, stout, thickened upward; perianth of 4 clawed segments, each with an upturned, oval blade; stamens 4, fused with the claws; pistils 4, sessile.
Fruits	Achenes obliquely obovoid, 2-2.8 mm. long including the short stylar beak, the dorsal keel well developed, the lateral ones obscure.

	Potamogeton gramineus	Potamogeton vaseyi
Flowering time	June-August
Habitat	Standing or running water.
Distribution	Occurring on both sides of the Cascades crest in Washington; Alaska to California, east to the Rocky Mountains, northern Great Plains, Great Lakes region, and eastern North America. [WildflowerSearch map] [BONAP county map]	[WildflowerSearch map] [BONAP county map]
Origin	Native
Conservation status	Not of concern
Sibling taxa	P. alpinus, P. amplifolius, P. berchtoldii, P. crispus, P. epihydrus, P. fibrillosus, P. foliosus, P. friesii, P. illinoensis, P. natans, P. nodosus, P. obtusifolius, P. praelongus, P. pusillus, P. richardsonii, P. robbinsii, P. strictifolius, P. zosteriformis	P. alpinus, P. amplifolius, 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	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 gramineus

Potamogeton vaseyi

grassy pondweed, variable pondweed

Habit

Aquatic, herbaceous perennials from slender rhizomes, the slender stems freely branching, sub-terete, up to 2 m. long.

Leaves

Leaves alternate, the submersed leaves sessile, linear to lanceolate or oblanceolate, 3-9 cm. long and 3-10 mm. broad, 3- to 7-nerved; floating leaves long-petiolate, elliptic to oblong-elliptic, 2-5 cm. long and 1-2 cm. broad, 13- to 19-nerved;

stipules open, firm, up to 3 cm. long.

Flowers

Flowers perfect, in 6-10 crowded whorls, in spikes 1.5-2.5 cm. long on peduncles 4-10 cm. long, stout, thickened upward;

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

stamens 4, fused with the claws;

pistils 4, sessile.

Fruits

Achenes obliquely obovoid, 2-2.8 mm. long including the short stylar beak, the dorsal keel well developed, the lateral ones obscure.

Potamogeton gramineus

Potamogeton vaseyi

Flowering time

June-August

Habitat

Standing or running water.

Distribution

Occurring on both sides of the Cascades crest in Washington; Alaska to California, east to the Rocky Mountains, northern Great Plains, Great Lakes region, and eastern North America.

[WildflowerSearch map]

[BONAP county map]

[WildflowerSearch map]

[BONAP county map]

Origin

Native

Conservation status

Not of concern

Sibling taxa