Burke: Potamogeton alpinus vs. Potamogeton epihydrus

	Potamogeton alpinus	Potamogeton epihydrus
	northern pondweed, reddish pondweed	ribbon-leaved pondweed
Habit	Annual, perennial herb, slender, rhizomed; stems greater than 100 cm, branched, branches not many, cylindric.	Aquatic, perennial herbs from slender rhizomes, the stems somewht flattened, simple or sparingly branched, 5-15 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.	Submersed leaves linear, sessile, 10-20 cm. long and 3-10 mm. broad, the mid-vein bordered by rows of air chambers; floating leaves with flattened petioles shorter than the blade, the blades firm, elliptic to oblong-elliptic, 4-8 cm. long and 10-20 mm. broad, 15- to 25-nerved; stipules free, 1-3 cm. long, blunt.
Flowers	Inflorescence generally < 3 cm, floating to emergent; peduncle stiff.	Flowers in dense spikes 2-4 cm. long, on peduncles 3-8 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 and broadly obovate, 3-4 mm. long, sharply keeled on the back.

	Potamogeton alpinus	Potamogeton epihydrus
Flowering time	June-August	June-August
Habitat	Calm water of lakes and slow streams.	Shallow to 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; Alaska to California, east to the Rocky Mountains; also in northeastern North America; Europe. [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. 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 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 epihydrus

northern pondweed, reddish pondweed

ribbon-leaved pondweed

Habit

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

Aquatic, perennial herbs from slender rhizomes, the stems somewht flattened, simple or sparingly branched, 5-15 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.

Submersed leaves linear, sessile, 10-20 cm. long and 3-10 mm. broad, the mid-vein bordered by rows of air chambers; floating leaves with flattened petioles shorter than the blade, the blades firm, elliptic to oblong-elliptic, 4-8 cm. long and 10-20 mm. broad, 15- to 25-nerved;

stipules free, 1-3 cm. long, blunt.

Flowers

Inflorescence generally < 3 cm, floating to emergent;

peduncle stiff.

Flowers in dense spikes 2-4 cm. long, on peduncles 3-8 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 and broadly obovate, 3-4 mm. long, sharply keeled on the back.

Potamogeton alpinus

Potamogeton epihydrus

Flowering time

June-August

Habitat

Calm water of lakes and slow streams.

Shallow to 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; Alaska to California, east to the Rocky Mountains; also in northeastern North America; Europe.

[WildflowerSearch map]

[BONAP county map]

Origin

Native

Conservation status

Not of concern

Sibling taxa