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alpine pondweed, northern pondweed, potamot alpin, reddish pondweed

Nuttall's ribbon-leaf pondweed, potamot emerge, ribbon-leaf pondweed

Cauline stems

terete, without spots, to 200 cm;

nodal glands absent.

flattened, without spots, 10–90 cm;

glands absent.

Turions

absent.

absent.

Leaves

submersed and floating or floating absent, ± spirally arranged.

both submersed and floating or floating absent, ± spirally arranged.

Floating leaves

petioles continuous in color to apex, 0.1–1.2 cm;

blade reddish green, elliptic or oblanceolate to obovate or oblong-linear, 4–7(–10) cm × 10–25(–40) mm, base gradually tapering into petiole, apex obtuse or acute;

veins (7–)9–13(–15).

petiolate;

petioles continuous in color to apex, 2–12.5 cm;

blade adaxially light green, narrowly oblong-oblanceolate to elliptic, 2–8 cm × 4–20 mm, base acute, apex rounded or bluntly cuspidate;

veins 11–41.

Submersed leaves

sessile, lax;

stipules persistent, inconspicuous, convolute, free from blade, light brown to reddish, not ligulate, (1.2–)1.5–2.5(–4) cm, not fibrous, not shredding at tip, apex blunt;

blade reddish green, oblong-linear to linear-lanceolate, not arcuate, 4.5–18(–25) cm × 5–20 mm, base rounded, without basal lobes, slightly clasping, margins entire, not crispate, apex not hoodlike, obtuse or acute, lacunae in 0–6 rows each side of midvein;

veins 7–9.

sessile, lax;

stipules persistent, inconspicuous, convolute, free from blade, red-brown, not ligulate, 1–3 cm, not fibrous, not shredding at tip, apex obtuse;

blade red-brown to light green, linear, not arcuate, 5–22 cm × 1–10 mm, base not clasping, without basal lobes, margins entire, not crispate, apex not hoodlike, blunt to acute, lacunae present, broad band each side of midvein;

veins 3–13.

Inflorescences

unbranched, emersed;

peduncles not dimorphic, terminal or axillary, erect, cylindric, 3–10(–16) cm;

spikes not dimorphic, cylindric, 10–35 mm.

unbranched, emersed;

peduncles not dimorphic, axillary, erect, cylindric, 1.5–5(–16) cm;

spikes not dimorphic, cylindric, 0.8–4 cm.

Fruits

pedicellate, tawny olive-green, obovoid, plump, turgid, abaxially keeled, laterally keeled or not, (2.5–)3–3.5 × (1.7–)2–2.4 mm, lateral keels when present without points;

beak abaxially curved, 0.5–0.9 mm;

sides without basal tubercles;

embryo with 1 full spiral.

sessile, greenish brown, round-obovoid, flattened, abaxially and laterally keeled, 2.5–4.5 × 2–3.6 mm, lateral keels without sharp points;

beak erect, 0.5 mm;

sides without basal tubercles;

embryo with less than 1 full spiral.

Rhizome(s)

present.

present.

2n

= 52.

= 26.

Potamogeton alpinus

Potamogeton epihydrus

Phenology Flowering early summer–fall. Flowering summer–fall.
Habitat Ponds, lakes, and slow-moving streams Still or flowing waters of lakes, ponds, streams, and rivers
Elevation 400–2500 m (1300–8200 ft) 10–1900 m (0–6200 ft)
Distribution
from FNA
AK; CA; CO; ID; MA; ME; MI; MN; MT; NH; NJ; NV; NY; OR; PA; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NL; NS; NT; NU; ON; PE; QC; SK; YT; Greenland; Europe; Asia Eurasia
[WildflowerSearch map]
[BONAP county map]
from FNA
AK; AL; CA; CO; CT; DE; FL; GA; IA; ID; IN; LA; MA; MD; ME; MI; MN; MS; MT; NC; NH; NJ; NY; OH; OR; PA; RI; SC; SD; TN; UT; VA; VT; WA; WI; WV; WY; BC; MB; NB; NL; NS; ON; PE; QC; SK; SPM; Europe
[WildflowerSearch map]
[BONAP county map]
Discussion

Plants of Potamogeton alpinus often are red whenever taken from the water, a feature that makes this species quite distinctive.

Two varieties, Potamogeton alpinus var. tenuifolius and var. subellipticus, have been recognized in North America, based mainly on submersed leaf shape. Plants bearing both leaf types have been observed in the same population; hence the varieties are not recognized.

Four hybrids, Potamogeton alpinus × P. nodosus (= P. ×subobtusus Hagström), P. alpinus × P. gramineus (= P. xnericius Hagström), P. alpinus × P. praelongus (= P. ×griffithii A. Bennett), and P. alpinus × P. perfoliatus (= P. ×prussicus Hagström), have been described.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

No specimens have been seen from Maryland, but the species is to be expected there.

Two varieties, Potamogeton epihydrus var. epihydrus and var. ramosus, have been recognized. These prove not to be distinct. Both varieties often grow in the same body of water in the same population. The wider-leaved plants often occur in more alkaline waters. Two hybrids, P. epihydrus var. nuttallii × P. gramineus and P. epihydrus × P. nodosus (= P. ×subsessilis Hagström), have been described.

Potamogeton epihydrus is a common species of lakes and streams of northern United States and southern Canada. It extends southward in the eastern United States to Louisiana and Alabama. Potamogeton epihydrus is one of our more easily recognized species: it has floating leaves, linear submersed leaves, and fruits with an embryo with one full spiral or less. The only other North American pondweed with a similar set of characteristics is P. tennesseensis, which differs from P. epihydrus by the former having long tapering apices in the submersed leaves whereas the latter has blunt to acute apices.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 22. FNA vol. 22.
Parent taxa Potamogetonaceae > Potamogeton Potamogetonaceae > Potamogeton
Sibling taxa
P. amplifolius, P. bicupulatus, P. clystocarpus, P. confervoides, P. crispus, P. diversifolius, P. epihydrus, P. floridanus, P. foliosus, P. friesii, P. gramineus, P. groenlandicus, P. hillii, P. illinoensis, P. natans, P. nodosus, P. oakesianus, P. oblongus, P. obtusifolius, P. ogdenii, P. perfoliatus, P. praelongus, P. pulcher, P. pusillus, P. richardsonii, P. robbinsii, P. spirillus, P. strictifolius, P. subsibiricus, P. tennesseensis, P. vaseyi, P. zosteriformis
P. alpinus, P. amplifolius, P. bicupulatus, P. clystocarpus, P. confervoides, P. crispus, P. diversifolius, P. floridanus, P. foliosus, P. friesii, P. gramineus, P. groenlandicus, P. hillii, P. illinoensis, P. natans, P. nodosus, P. oakesianus, P. oblongus, P. obtusifolius, P. ogdenii, P. perfoliatus, P. praelongus, P. pulcher, P. pusillus, P. richardsonii, P. robbinsii, P. spirillus, P. strictifolius, P. subsibiricus, P. tennesseensis, P. vaseyi, P. zosteriformis
Synonyms P. alpinus subsp. tenuifolius, P. alpinus var. subellipticus, P. alpinus var. tenuifolius, P. tenuifolius, P. tenuifolius var. subellipticus P. epihydrus subsp. nuttallii, P. epihydrus var. ramosus
Name authority Balbis: Misc. Bot. 13. (1804) Rafinesque: Medical Repository 5: 354. 1808, hexade hexade 2; 3; 2:409. (1811)
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