Burke: Potamogeton alpinus vs. Potamogeton pusillus

	Potamogeton alpinus	Potamogeton pusillus
	northern pondweed, reddish pondweed	small 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 very slender, freely branched, up to 10 dm. 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, submersed, narrowly linear, up to 7 cm. long and 0.5-2 mm. broad, 3-nerved, acute, bordered at the base with small, globose glands; stipules 6-15 mm. long, surrounding the stem for half their length.
Flowers	Inflorescence generally < 3 cm, floating to emergent; peduncle stiff.	Flowers perfect, in spikes 3-15 cm. long but with only 1-3 whorls, on very slender peduncles 1.5-4 cm. long; 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, about 2 mm. long, not keeled, the stylar beak 0.5 mm. long, slightly recurved.

	Potamogeton alpinus	Potamogeton pusillus
Flowering time	June-August	July - August
Habitat	Calm water of lakes and slow streams.	Shallow ponds and streams.
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]	British Columbia south on both sides of the Cascades to California, east to the Atlantic. [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. nodosus, P. obtusifolius, P. praelongus, 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 pusillus

northern pondweed, reddish pondweed

small 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 very slender, freely branched, up to 10 dm. 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, submersed, narrowly linear, up to 7 cm. long and 0.5-2 mm. broad, 3-nerved, acute, bordered at the base with small, globose glands;

stipules 6-15 mm. long, surrounding the stem for half their length.

Flowers

Inflorescence generally < 3 cm, floating to emergent;

peduncle stiff.

Flowers perfect, in spikes 3-15 cm. long but with only 1-3 whorls, on very slender peduncles 1.5-4 cm. long;

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, about 2 mm. long, not keeled, the stylar beak 0.5 mm. long, slightly recurved.

Potamogeton alpinus

Potamogeton pusillus

Flowering time

June-August

July - August

Habitat

Calm water of lakes and slow streams.

Shallow ponds and streams.

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]