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

big-leaf pondweed, broad-leaf pondweed, large-leaf pondweed, potamot à grandes feuilles

Rhizomes

absent.

present.

Cauline stems

compressed, without spots, 10–135 cm;

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

terete, often rusty spotted, 6–110 cm;

nodal glands absent.

Turions

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.

absent.

Leaves

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).

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

Floating leaves

petioles continuous in color to apex, 2.3–22.6 cm;

blade adaxially light green, lanceolate to round elliptic, 4.3–9.2 cm × 25–38 mcm, base rounded to cordate, apex acute to rounded;

veins 27–49.

Submersed leaves

petiolate, lax;

stipules persistent, conspicuous, convolute, free from blade, light brown, not ligulate, 1.5–11.7 cm, not fibrous, not shredding at tip, apex acute;

petioles terete, 0.9–11.5 cm;

blade light to dark green, ovate to oblanceolate, distinctly arcuate, 5–12.5 cm × 15–58 mm, base rounded to acute, without basal lobes, not clasping, margins entire, crispate, apex not hoodlike, acute to round-apiculate, lacunae absent;

veins 19–49.

Inflorescences

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.

unbranched, emersed;

peduncles not dimorphic, terminal or axillary, erect, cylindric, 4.5–22.3 cm;

spikes not dimorphic, cylindric, 34–65 mm.

Fruits

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.

sessile, reddish brown, obovoid, turgid, abaxially keeled, laterally ridged, 5–6.7 × 4.5–5.2 mm, lateral ridges without points;

beak erect, 0.5–0.8 mm;

sides without basal tubercles;

embryo with full spiral.

2n

= 26.

= 52.

Potamogeton friesii

Potamogeton amplifolius

Phenology Flowering and fruiting summer–fall. Flowering summer–fall.
Habitat Calcareous to brackish waters of lakes and slow-flowing streams Waters of lakes, ponds, streams, and rivers
Elevation 0–3100 m (0–10200 ft) 0–1900(–2900) m (0–6200(–9500) ft)
Distribution
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]
from FNA
AL; AR; CA; CT; GA; IA; ID; IL; IN; KS; MA; MD; ME; MI; MN; MO; MT; NC; NE; NH; NJ; NY; OH; OK; OR; PA; RI; SD; TN; VA; VT; WA; WI; WV; WY; BC; MB; NB; NF; NS; ON; QC; SK
[WildflowerSearch map]
[BONAP county map]
Discussion

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.)

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

Potamogeton amplifolius is common throughout much of North America. Its submersed leaves are larger than those of most other species of Potamogeton, are arcuate, and have more veins than do any other species.

One hybrid, Potamogeton amplifolius × P. illinoensis (= P. × scoliophyllus Hagström), has 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. 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
P. alpinus, 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
Name authority Ruprecht: Hist. Stirp. Fl. Petrop. 43. (1845) Tuckerman: American Journal of Science, and Arts ser. 2, 6:225. (1848)
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