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

potamot de Vasey, Vasey's pondweed

Rhizomes

present.

absent.

Cauline stems

terete, often rusty spotted, 6–110 cm;

nodal glands absent.

terete, without spots, 2–5 cm;

glands absent.

Turions

absent.

common, axillary, 0.5–2 cm × 0.5–1.2 mm, soft;

leaves ± 2-ranked;

outer leaves 2–3 per side, base not corrugate, apex acute;

inner leaves undifferentiated or rolled into tight, hardened structure.

Leaves

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

submersed, or both submersed and floating, ± 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.

petioles continuous in color to apex, 5–25 mm;

blade adaxially greenish brown, elliptic, spatulate, or obovate, 0.6–1.5 cm × 3–8 mm, base acute, apex obtuse;

veins 5–9.

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.

sessile, delicate;

stipules persistent, inconspicuous, convolute, free from blade, green to brown, not ligulate, 0.4–1.2 cm, not fibrous, not shredding at tip, apex attenuate;

blade light green, linear-filiform, not arcuate, 2–8 cm × 0.1–1 mm, bases slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to almost bristle-tipped, lacunae present, rarely absent, 0–2 rows each side of midvein;

veins 1(–3).

Inflorescences

unbranched, emersed;

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

spikes not dimorphic, cylindric, 34–65 mm.

unbranched, emersed;

peduncles not dimorphic, terminal, ascending in flower, recurved in fruit, cylindric, 5–30 mm;

spikes not dimorphic, cylindric or moniliform, 6–8 mm.

Fruits

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.

sessile, green to brown, obliquely round-obovoid, compressed, abaxially keeled, not laterally keeled, 1.5–2.5 × 1.2–1.6 mm;

beak erect, 0.3–0.5 mm;

sides without basal tubercles;

embryo with 1 full spiral.

2n

= 52.

= 28.

Potamogeton amplifolius

Potamogeton vaseyi

Phenology Flowering summer–fall. Flowering and fruiting summer–fall.
Habitat Waters of lakes, ponds, streams, and rivers Quiet waters of lakes, ponds, and rivers
Elevation 0–1900(–2900) m (0–6200(–9500) ft) 50–500 m (200–1600 ft)
Distribution
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]
from FNA
CT; IA; IL; IN; MA; ME; MI; MN; NH; NJ; NY; OH; PA; RI; VT; WI; NB; ON; QC
[WildflowerSearch map]
[BONAP county map]
Discussion

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.)

All of the original material of Potamogeton lateralis Morong, including the collection designated as the lectotype, has been studied (C. B. Hellquist et al. 1988). Every specimen, was a mixed collection of P. pusillus and P. vaseyi. Based on the results of the study, P. lateralis is taxonomically nomenclaturally invalid and should be rejected.

Potamogeton vaseyi is an uncommon species that has submersed leaves very similar to P. pusillus subsp. gemmiparus. Floating leaves apparently are present only when the species is fertile, and the species often grows intermixed with that subspecies. Collections are consequently often a mixture of the two taxa. Also, sterile collections of either taxon can easily be mistaken for the other.

(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. 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
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. pulcher, P. pusillus, P. richardsonii, P. robbinsii, P. spirillus, P. strictifolius, P. subsibiricus, P. tennesseensis, P. zosteriformis
Name authority Tuckerman: American Journal of Science, and Arts ser. 2, 6:225. (1848) J. W. Robbins: in A. Gray, Manual of Botany of the Northern United States (ed. 5) 485. (1867)
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