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

flat-stalk pondweed, Fries' pondweed, potamot de Fries

Rhizomes

present.

absent.

Cauline stems

flattened, without spots, 10–90 cm;

glands absent.

compressed, without spots, 10–135 cm;

glands green, greenish brown, or gold, to 0.7 mm diam.

Turions

absent.

terminal or lateral, common, 1.5–5 cm × 1.5–4 mm, soft;

leaves ± 4-ranked;

outer leaves 2–3 per side, base corrugate, apex apiculate to acute;

inner leaves reduced, arranged into fan-shaped structure and oriented at 90° angles to outer leaves.

Leaves

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

submersed, ± spirally arranged, delicate to rigid, sessile;

stipules not persistent, inconspicuous, convolute, free from blade, white, not ligulate, 0.55–2.1 cm, fibrous, coarse, shredding at tip, apex obtuse;

blade light green, rarely olive-green to.somewhat reddish, linear, not arcuate, 2.3–6.5 cm × 1.2–3.2 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to apiculate, lacunae absent or 1 narrow row each side of midrib;

veins 5–7(–9).

Floating leaves

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, 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, axillary, erect, cylindric, 1.5–5(–16) cm;

spikes not dimorphic, cylindric, 0.8–4 cm.

unbranched, emersed;

peduncles not dimorphic, terminal or axillary, erect or rarely recurved, slightly clavate, 1.2–4.1(–7) cm;

spike not dimorphic, cylindric, 7–16 mm.

Fruits

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.

sessile, olive-green to brown, obovoid, turgid, not abaxially or laterally keeled, 1.8–2.5 × 1.2–2 mm;

beak erect, 0.3–0.7 mm;

sides without basal tubercles;

embryo with 1 full spiral.

2n

= 26.

= 26.

Potamogeton epihydrus

Potamogeton friesii

Phenology Flowering summer–fall. Flowering and fruiting summer–fall.
Habitat Still or flowing waters of lakes, ponds, streams, and rivers Calcareous to brackish waters of lakes and slow-flowing streams
Elevation 10–1900 m (0–6200 ft) 0–3100 m (0–10200 ft)
Distribution
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]
from FNA
AK; CO; CT; IA; ID; IL; IN; MA; ME; MI; MN; MT; ND; NE; NH; NY; OH; PA; RI; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NF; NS; NT; ON; PE; QC; SK; YT; Eurasia
[WildflowerSearch map]
[BONAP county map]
Discussion

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.)

Potamogeton friesii is a fairly common linear-leaved species, especially of calcareous waters of lakes and streams of the upper Midwest. Whenever turions are present, the species is easily identified, as it is the only one with the outer leaves of the turions having corrugate bases and the inner leaves turned at right angles to the outer leaves.

Two hybrids, Potamogeton friesii × P. pusillus (= P. × pusilliformis Fischer [P. × intermedius Fischer]) and P. friesii × P. obtusifolius (= P. × semifructus A. Bennett ex Ascherson & Graebner), have been described.

(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. 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
P. alpinus, P. amplifolius, P. bicupulatus, P. clystocarpus, P. confervoides, P. crispus, P. diversifolius, P. epihydrus, P. floridanus, P. foliosus, 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. epihydrus subsp. nuttallii, P. epihydrus var. ramosus
Name authority Rafinesque: Medical Repository 5: 354. 1808, hexade hexade 2; 3; 2:409. (1811) Ruprecht: Hist. Stirp. Fl. Petrop. 43. (1845)
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