Burke: Potamogeton alpinus vs. Potamogeton gramineus

	Potamogeton alpinus	Potamogeton gramineus
	northern pondweed, reddish pondweed	grassy pondweed, variable pondweed
Habit	Annual, perennial herb, slender, rhizomed; stems greater than 100 cm, branched, branches not many, cylindric.	Aquatic, herbaceous perennials from slender rhizomes, the slender stems freely branching, sub-terete, up to 2 m. long.
Leaves	Various shades of red; submersed sessile, 2-8 x 1-2 cm, lanceolate to elliptic-oblong, tapered to both ends, entire, tip blunt, veins 7-9; floating 0 or short-petioled, lanceolate, base tapered, veins 7-15; stipules beyond 3 cm, free, membranous, early-deciduous.	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	Inflorescence generally < 3 cm, floating to emergent; peduncle stiff.	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.
Fruit(s)	Around 2.5 mm, keels 1 or 3, generally, beaked, sides concave to convex.	Achenes obliquely obovoid, 2-2.8 mm. long including the short stylar beak, the dorsal keel well developed, the lateral ones obscure.

	Potamogeton alpinus	Potamogeton gramineus
Flowering time	June-August	June-August
Habitat	Calm water of lakes and slow streams.	Standing or running water.
Distribution	Occurring on both sides of the Cascades crest in Washington; Alaska to California, east to the Rocky Mountains and northern Great Plains; also in eastern North America. [WildflowerSearch map] [BONAP county map]	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]
Origin	Native	Native
Conservation status	Not of concern	Not of concern
Sibling taxa	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	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
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 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

Potamogeton gramineus

northern pondweed, reddish pondweed

grassy pondweed, variable pondweed

Habit

Annual, perennial herb, slender, rhizomed; stems greater than 100 cm, branched, branches not many, cylindric.

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

Leaves

Various shades of red; submersed sessile, 2-8 x 1-2 cm, lanceolate to elliptic-oblong, tapered to both ends, entire, tip blunt, veins 7-9; floating 0 or short-petioled, lanceolate, base tapered, veins 7-15;

stipules beyond 3 cm, free, membranous, early-deciduous.

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

Inflorescence generally < 3 cm, floating to emergent;

peduncle stiff.

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.

Fruit(s)

Around 2.5 mm, keels 1 or 3, generally, beaked, sides concave to convex.

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

Potamogeton alpinus

Potamogeton gramineus

Flowering time

June-August

Habitat

Calm water of lakes and slow streams.

Standing or running water.

Distribution

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

[WildflowerSearch map]

[BONAP county map]

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]

Origin

Native

Conservation status

Not of concern

Sibling taxa