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clasping-leaf pondweed, potamot perfolié

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

Rhizomes

present.

absent.

Cauline stems

terete, without spots, to 250 cm;

nodal 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

submersed, ± spirally arranged, sessile, lax;

stipules deteriorating into fibers and deciduous, inconspicuous (absent on proximal portion of stem), convolute, free from blade, light brown to green, not ligulate, 3.5–6.5 cm, not fibrous, not shredding at apex;

blade olive-green, broadly lanceolate, orbiculate, or ovate, not arcuate, 0.9–7.6(–9.7) cm × 7–40 mm, base rounded, without basal lobes, clasping, margins entire, often crispate, apex not hoodlike, not splitting when pressed, round, rarely acute;

veins 3–25.

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).

Inflorescences

unbranched, emersed;

peduncles not dimorphic, terminal or axillary, erect to rarely recurved, cylindric, 1–7.3 cm;

spike not dimorphic, cylindric, 0.4–4.8 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 to olive-green, obovoid, turgid or rarely concave, not abaxially or laterally keeled, 1.6–3 × 1.3–2.2 mm;

beak erect, 0.4–0.6 mm;

sides without basal tubercles;

embryo with 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

= 52.

= 26.

Potamogeton perfoliatus

Potamogeton friesii

Phenology Flowering summer–fall. Flowering and fruiting summer–fall.
Habitat Waters, often brackish, of lakes, streams, rivers, and bays Calcareous to brackish waters of lakes and slow-flowing streams
Elevation 0–100 m (0–300 ft) 0–3100 m (0–10200 ft)
Distribution
from FNA
AL; CT; DC; DE; FL; LA; MA; MD; ME; NC; NH; NJ; NY; OH; PA; RI; VA; VT; NB; NL; NS; ON; PE; QC; SPM; Africa; Greenland; Eurasia; Central America (Guatemala); Australia
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[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

Four hybrids, Potamogeton perfoliatus × P. praelongus (= P. × cognatus Ascherson & Graebner), P. perfoliatus × P. pusillus (= P. × mysticus Morong), P. gramineus × P. perfoliatus (= P. × nitens Weber [P. × subnitens Hagström]), and P. alpinus × P. perfoliatus (= P. × prussicus Hagström), have been described.

(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. 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. 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
Name authority Linnaeus: Sp. Pl. 1: 126. 1753 (as perfoliatum) Ruprecht: Hist. Stirp. Fl. Petrop. 43. (1845)
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