Burke: Potamogeton alpinus vs. Potamogeton obtusifolius

	Potamogeton alpinus	Potamogeton obtusifolius
	northern pondweed, reddish pondweed	blunt-leaved pondweed
Habit	Annual, perennial herb, slender, rhizomed; stems greater than 100 cm, branched, branches not many, cylindric.	Annual, perennial herb, slender, rhizomes absent; cauline stems slightly compressed, 35-90 cm, without spots; glands yellow-green to gold, 0.2-1 mm diameter; turions terminal, abundant, 3.5-7.8 cm x 2.3--5.1 mm, soft.
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 2-ranked; outer leaves 3-4 per side, base not corrugate, apex apiculate to obtuse; inner leaves undifferentiated; leaves submersed, often spirally arranged, sessile, flaccid; stipules persistent, inconspicuous, convolute, free from blade, not ligulate, white, 0.6-1.8 cm, fibrous, rarely shredding at tip, apex obtuse; blade light green to somewhat reddish, linear, not arcuate, 3-8.2 cm x 1--3.5 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, obtuse or round-apiculate, lacunae in 1-3 rows each side of midrib; veins 3.
Flowers	Inflorescence generally < 3 cm, floating to emergent; peduncle stiff.
Fruit	Around 2.5 mm, keels 1 or 3, generally, beaked, sides concave to convex.	Fruits sessile, olive-green to brown, obovoid, turgid, abaxially keeled or not, laterally keeled or not, 2.5--3.6 x 1.7--2.4 mm, lateral keels without points; beak erect, 0.8-1 mm; sides without basal tubercles; embryo with 1 full spiral.

	Potamogeton alpinus	Potamogeton obtusifolius
Flowering time	June-August	June-August
Habitat	Calm water of lakes and slow streams.	Lakes, slow streams, and alkaline 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 west of the Cascades crest in Washington; Alaska to Washington, east across the northern U.S. and Canada to the Atlantic Coast. [WildflowerSearch map] [BONAP county map]
Origin	Native	Native
Conservation status	Not of concern	Sensitive in Washington (WANHP)
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. 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, WA Local Web sites: 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 obtusifolius

northern pondweed, reddish pondweed

blunt-leaved pondweed

Habit

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

Annual, perennial herb, slender, rhizomes absent; cauline stems slightly compressed, 35-90 cm, without spots; glands yellow-green to gold, 0.2-1 mm diameter; turions terminal, abundant, 3.5-7.8 cm x 2.3--5.1 mm, soft.

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 2-ranked; outer leaves 3-4 per side, base not corrugate, apex apiculate to obtuse; inner leaves undifferentiated;

leaves submersed, often spirally arranged, sessile, flaccid;

stipules persistent, inconspicuous, convolute, free from blade, not ligulate, white, 0.6-1.8 cm, fibrous, rarely shredding at tip, apex obtuse;

blade light green to somewhat reddish, linear, not arcuate, 3-8.2 cm x 1--3.5 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, obtuse or round-apiculate, lacunae in 1-3 rows each side of midrib;

veins 3.

Flowers

Inflorescence generally < 3 cm, floating to emergent;

peduncle stiff.

Fruit

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

Fruits sessile, olive-green to brown, obovoid, turgid, abaxially keeled or not, laterally keeled or not, 2.5--3.6 x 1.7--2.4 mm, lateral keels without points;

beak erect, 0.8-1 mm;

sides without basal tubercles;

embryo with 1 full spiral.

Potamogeton alpinus

Potamogeton obtusifolius

Flowering time

June-August

Habitat

Calm water of lakes and slow streams.

Lakes, slow streams, and alkaline 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]