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heartleaf pondweed, potamot gracieux, spotted pondweed

grass-leaf pondweed, grassy pondweed, potamot à feuilles de graminées, variable pondweed, variable-leaf pondweed

Rhizomes

present.

present.

Cauline stems

terete, conspicuously spotted, 8–95 cm;

nodal glands absent.

terete to flattened, without spots, to 150 cm;

nodal glands absent.

Turions

absent.

absent.

Leaves

both submersed and floating, ± spirally arranged.

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

Floating leaves

petioles continuous in color to apex, 1–16.5 cm;

blade adaxially light to dark green, lanceolate to round-ovate, 2.5–8.5 cm × 11–44 mm, base rounded to cordate, apex acute to rounded;

veins 15–21.

petioles continuous in color to apex, 3–4.5 cm;

blade yellow-green to dark green, elliptic to ovate, 3.5–4 cm × 16–20 mm, base rounded, apex acuminate;

veins 11–13.

Submersed leaves

petiolate, lax;

stipules deliquescent, inconspicuous, convolute, free from blade, light to dark brown, not ligulate, 0.7–1.2 cm, not fibrous, not shredding at tip, apex obtuse;

petioles 0.5–4.5 cm;

blade dark green, linear-lanceolate to lanceolate, often arcuate, 3.5–13.8 cm × 60–165 mm acute, base acute to rounded, without basal lobes, margins entire, crispate, apex not hoodlike, acute to obtuse, lacunae in 2–5 rows each side of midrib;

veins 7–19.

sessile or rarely petiolate, lax;

stipules persistent, inconspicuous, convolute, free from blade, pale green to brown, not ligulate, 1.3–1.6 cm, not fibrous, not shredding at tip, apex acute to obtuse;

petioles to 3 cm;

blade light green to brownish green, elliptic, not arcuate, 3.1–9.1 cm × 3–27 mm, base attenuate, without basal lobes, not clasping, margins entire, rarely crispate, apex not hoodlike, acuminate, lacunae in 1–2 rows each side of midvein;

veins 3–9.

Inflorescences

unbranched, emersed;

peduncles not dimorphic, terminal or axillary, erect to ascending, cylindric, 3.3–9.4 cm;

spikes not dimorphic, cylindric, 17–36 mm.

emersed, unbranched;

peduncles not dimorphic, both axillary and terminal, erect to ascending, cylindric, 3.2–7.7 cm;

spikes not dimorphic, cylindric, 15–35 mm.

Fruits

sessile, dark green to dark brown, ovoid to obovoid, turgid, abaxially keeled, laterally ridged, 5–6.5 × 4.1–5 mm, lateral ridges without points;

beak erect, 0.5 mm;

embryo with 1 full spiral.

sessile, greenish brown, ovoid, laterally compressed, abaxially and laterally keeled, 1.9–2.3 × 1.8–2 mm, lateral keels without points;

beak erect, 0.3–0.5 mm;

sides without basal tubercles;

embryo with less than 1 full spiral.

Chromosome number

apparently unknown not available.

2n

= 52.

Potamogeton pulcher

Potamogeton gramineus

Phenology Flowers summer–fall. Flowering summer–fall.
Habitat Stagnant to slow-flowing waters of streams, lakes, ponds, and small rivers Ponds, lakes, streams, and rivers
Elevation 0–700 m (0–2300 ft) 0–3500 m (0–11500 ft)
Distribution
from FNA
AL; AR; CT; DE; FL; GA; IL; IN; KY; LA; MA; MD; ME; MI; MN; MO; MS; NC; NH; NJ; NY; OH; OK; PA; RI; SC; TN; TX; VA; WI; WV; NB; NS; PE; Ont
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from FNA
AK; AZ; CA; CO; CT; IA; ID; IL; IN; KS; KY; MA; MD; ME; MI; MN; MT; ND; NE; NH; NJ; NV; NY; OH; OR; PA; RI; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NL; NS; NT; NU; ON; PE; QC; SK; YT; SPM; Greenland; Eurasia
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Discussion

Potamogeton pulcher is similar in morphology to P. amplifolius and occurs in similar habitats. Potamogeton pulcher differs from P. amplifolius by the former having lanceolate to linear-lanceolate submersed leaves with fewer than 19 veins, whereas the latter has ovate submersed leaves with more than 19 veins.

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

Seven hybrids, Potamogeton gramineus × P. nodosus (= P. × argutulus Hagström), P. gramineus × P. richardsonii (= P. hagstroemii A. Bennett [as hagstromii]), P. alpinus × P. gramineus (= P. × nericius Hagström), P. gramineus × P. perfoliatus (= P. × nitens Weber [P. × subnitens Hagström]), P. gramineus × P. natans (= P. × sparganiifolius Laestadius ex Fries), P. gramineus × P. illinoensis [= P. × spathuliformis (J. W. Robbins) Morong)], and P. gramineus × P. praelongus (= P. × vilnensis Galinis), have been described.

Three varieties were recognized (E. C. Ogden 19435) and treated (M. L. Fernald 1950). These varieties, Potamogeton gramineus var. gramineus, deletion}P. gramineus var. myriophyllus, and P. gramineus var. maximus, were said to be separated by the shape and size of the submersed leaves. We have studied many populations of this species in the field and have observed on several occasions that a single population has leaf morphology variable enough to include all three varieties. We have, , therefore, chosen not to recognize any infraspecific categories for this species.

(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. praelongus, 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. 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. gramineus var. maximus, P. gramineus var. myriophyllus
Name authority Tuckerman: American Journal of Science, and Arts 45:38. (1843) Linnaeus: Sp. Pl. 1: 127. 1753 (as gramineum)
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