Burke: Potamogeton alpinus vs. Potamogeton foliosus

	Potamogeton alpinus	Potamogeton foliosus
	northern pondweed, reddish pondweed	leafy 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 freely branching, somewhat compressed and narrow winged, scarcely 1 mm. broad, 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 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.
Flowers	Inflorescence generally < 3 cm, floating to emergent; peduncle stiff.	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.
Fruit(s)	Around 2.5 mm, keels 1 or 3, generally, beaked, sides concave to convex.	Achenes obliquely obovoid, 2 mm. long, with a prominent dorsal keel.

	Potamogeton alpinus	Potamogeton foliosus
Flowering time	June-August	June-August
Habitat	Calm water of lakes and slow streams.	Standing to moving, shallow 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 across North America 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. 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 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 foliosus

northern pondweed, reddish pondweed

leafy 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 freely branching, somewhat compressed and narrow winged, scarcely 1 mm. broad, 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 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.

Flowers

Inflorescence generally < 3 cm, floating to emergent;

peduncle stiff.

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.

Fruit(s)

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

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

Potamogeton alpinus

Potamogeton foliosus

Flowering time

June-August

Habitat

Calm water of lakes and slow streams.

Standing to moving, shallow 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]