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long-stalk pondweed, potamot à longs pédoncules, white-stalk pondweed, white-stem pondweed

clasping-leaf pondweed, potamot perfolié

Cauline stems

terete, without spots, to 210 cm;

nodal glands absent.

terete, without spots, to 250 cm;

nodal glands absent.

Turions

absent.

absent.

Leaves

submersed, ± spirally arranged, sessile, lax;

stipules persistent, conspicuous, convolute, free from blade, white to green, not ligulate, 3–8.1 cm, fibrous, shredding at apex;

blade pale green, rarely olive green, linear-lanceolate, not arcuate, 0.8–2.8 cm × 11–46 mm, base clasping, without basal lobes, margins entire, rarely crispate, apex hoodlike, splitting when pressed, obtuse, lacunae absent;

veins 11–33.

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.

Inflorescences

emersed, unbranched;

peduncles not dimorphic, terminal or axillary, erect to spreading, cylindric, 9.5–53 cm;

spikes not dimorphic, cylindric, 34–75 mm.

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.

Fruits

sessile, greenish brown, obovoid, turgid, abaxially keeled, occasionally laterally keeled, 4–5.7 × 3.2–4 mm, lateral keels when present without points;

beak erect, 0.6–1 mm;

sides without basal tubercles;

embryo with 1 full spiral.

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.

Rhizome(s)

present.

present.

2n

= 52.

= 52.

Potamogeton praelongus

Potamogeton perfoliatus

Phenology Flowering summer–fall. Flowering summer–fall.
Habitat Neutral to alkaline waters of lakes, rivers, and streams Waters, often brackish, of lakes, streams, rivers, and bays
Elevation Greenland; 100–3000 m (Greenland; 300–9800 ft) 0–100 m (0–300 ft)
Distribution
from FNA
AK; CA; CO; CT; IA; ID; IN; MA; ME; MI; MN; MT; NE; NH; NJ; NY; OR; PA; SD; UT; VT; WI; WY; AB; BC; MB; NB; NF; NS; NT; NU; ON; PE; QC; SK; YT; Mexico; Greenland; Eurasia
[WildflowerSearch map]
[BONAP county map]
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
[WildflowerSearch map]
[BONAP county map]
Discussion

Potamogeton praelongus is one of the easiest pondweeds to identify with its submersed leaves only clasping the more or less zigzagged stem. The persistent, hugelarge, white stipules provide another clue to this species.

Four hybrids, Potamogeton perfoliatus × P. praelongus (= P. × cognatus Ascherson & Graebner), P. alpinus × P. praelongus (= P. × griffithii A. Bennett), P. crispus × P. praelongus (= P. × undulatus Wolfgang ex Schultes & Schultes f.), and P. gramineus × P. praelongus (= P. × vilnensis Galinus), have been described.

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

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.)

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. perfoliatus, 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. 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
Name authority Wulfen: Arch. Bot. (Leipzig) 3: 331. (1805) Linnaeus: Sp. Pl. 1: 126. 1753 (as perfoliatum)
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