Burke: Potamogeton alpinus vs. Potamogeton nodosus

	Potamogeton alpinus	Potamogeton nodosus
	northern pondweed, reddish pondweed	loddon's pondweed, long-leaved pondweed
Habit	Annual, perennial herb, slender, rhizomed; stems greater than 100 cm, branched, branches not many, cylindric.	Aquatic, herbaceous perennials from slender rhizomes, the stems sub-terete, sparingly branched, 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 with petioles 2-10 cm. long, the blades lanceolate-elliptic, 10-20 cm. long and 1-2 cm. broad, thin; floating leaves leathery, long-petiolate, elliptic, 5-12 cm long and 2-4 cm. broad; stipules 4-8 cm. long.
Flowers	Inflorescence generally < 3 cm, floating to emergent; peduncle stiff.	Flowers perfect, in densely-flowered spikes with up to 15 whorles, 2-6 cm. long; peduncles thicker than the stems; 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 obovoid, 3-4 mm. long, with a sharp dorsal keel and prominent lateral keels.

	Potamogeton alpinus	Potamogeton nodosus
Flowering time	June-August	June-August
Habitat	Calm water of lakes and slow streams.	Shallow to rather deep 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; British Columbia to Mexico; east over most of the United States to the Atlantic Coast. [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. gramineus, P. illinoensis, P. natans, 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 nodosus

northern pondweed, reddish pondweed

loddon's pondweed, long-leaved pondweed

Habit

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

Aquatic, herbaceous perennials from slender rhizomes, the stems sub-terete, sparingly branched, 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 with petioles 2-10 cm. long, the blades lanceolate-elliptic, 10-20 cm. long and 1-2 cm. broad, thin; floating leaves leathery, long-petiolate, elliptic, 5-12 cm long and 2-4 cm. broad;

stipules 4-8 cm. long.

Flowers

Inflorescence generally < 3 cm, floating to emergent;

peduncle stiff.

Flowers perfect, in densely-flowered spikes with up to 15 whorles, 2-6 cm. long;

peduncles thicker than the stems;

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 obovoid, 3-4 mm. long, with a sharp dorsal keel and prominent lateral keels.

Potamogeton alpinus

Potamogeton nodosus

Flowering time

June-August

Habitat

Calm water of lakes and slow streams.

Shallow to rather deep 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]