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small pondweed

closed-leaf pondweed, leafy pondweed

Rhizomes

absent.

absent.

Cauline stems

terete to slightly compressed, without spots, 18–150 cm;

glands present on at least some nodes, green, gold, brown, or rarely white, to 0.5 mm diam.

slightly compressed, without spots, 4–75 cm;

glands rarely present, black to gold, to 0.5 mm diam.

Turions

common, soft, lateral or terminal, 0.9–3.2 cm × 0.3–1.8 mm, soft;

leaves ± 2-ranked;

outer leaves 1–3 per side, base not corrugate, apex subulate to obtuse;

inner leaves rolled into hardened fusiform structure.

uncommon, lateral or terminal, 0.9–2.5 cm × 0.6–2 mm, soft;

outer leaves 1–3 per side, base not corrugate, apex acute to apiculate;

inner leaves rolled into hardened fusiform structure.

Leaves

submersed, ± spirally arranged, sessile, delicate to coarse;

stipules persistent, inconspicuous, connate or convolute, free from base of blade, brown to green or white, not ligulate, 0.31–0.92 cm, rarely appearing fibrous, not shredding at tip, apex obtuse;

blade pale green to olive-green, rarely somewhat reddish, linear, not arcuate, 0.9–6.5 cm × 0.2–2.5 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, subulate to obtuse, lacunae absent or present, in 0–5 rows each side of midrib;

veins 1–3(–5).

submersed, ± spirally arranged, sessile, delicate;

stipules persistent, inconspicuous, convolute, free from blade, greenish to brown or rarely white, not ligulate, 0.2–2.2 cm, delicate to fibrous, rarely shredding at tip, apex obtuse;

blade pale green to olive-green, rarely somewhat reddish, linear, not arcuate, 1.3–8.2 cm × 0.3–2.3 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to apiculate, rarely with bristle, lacunae rarely present, 0–2 rows each side of midrib;

veins 1–3(–5).

Inflorescences

unbranched, submersed or emersed;

peduncles not dimorphic, axillary or terminal, erect, rarely recurved, filiform to slightly clavate, 0.5–6.2(–6.6) cm;

spikes not dimorphic, capitate to cylindric, 1.5–10.1 mm.

unbranched, emersed;

peduncles not dimorphic, in axils of proximal, rarely distal leaves, recurved, clavate, 0.3–1.1(–3.7) cm;

spikes not dimorphic, capitate to cylindric, 1.5–7 mm.

Fruits

sessile, green to brown, ovoid to obovoid, turgid to concave, not abaxially or laterally keeled, 1.5–2.2 × 1.2–1.6 mm;

beak erect, 0.1–0.6;

sides without basal tubercles;

embryo with less than 1 full spiral.

pale green to olive-green or brown, obovate to nearly orbicular, turgid to concave, sessile, abaxially keeled, not laterally keeled, 1.4–2.7 × 1.1–2.2 mm, abaxial keel undulate, winglike;

beak erect, 0.2–0.6 mm;

sides without basal tubercles;

embryo with 1 full spiral.

Potamogeton pusillus

Potamogeton foliosus

Distribution
from FNA
AK; AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NS; NT; NU; ON; PE; QC; SK; YT; nearly worldwide
[WildflowerSearch map]
[BONAP county map]
from FNA
AK; AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NS; NT; ON; PE; QC; SK; YT; Central America
[WildflowerSearch map]
[BONAP county map]
Discussion

Three hybrids, Potamogeton perfoliatus × P. pusillus (= P. × mysticus Morong), P. friesii × P. pusillus (= P. × pusilliformis Fisher [P. × intermedius Fischer]), and P. obtusifolius × P. pusillus (= P. × saxonicus Hagström), have been described.

Subspecies 3 (3 in the flora).

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

Subspecies 2 (2 in the flora).

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

Key
1. Leaf blade 1-veined, subulate, 0.2–0.7 mm wide; New England and s Quebec.
subsp. gemmiparus
1. Leaf blade 1–5-veined, acute to obtuse, 0.2–2.5 mm wide; widespread throughout North America.
→ 2
2. Mature fruits obovoid, sides concave; beak toward adaxial edge, rarely median; peduncles filiform to cylindric, 1–3 per plant; inflorescences interrupted; leaf blade with 0–2 rows of lacunae along midrib, apex acute, rarely apiculate, rarely with bristle; stipules connate.
subsp. pusillus
2. Mature fruits widest at middle or ovoid, sides rounded; beak median, not toward adaxial edge; peduncles cylindric, more than 3 per plant; inflorescences continuous; leaf blade with 1–5 rows of lacunae along midrib, apex acute to obtuse; stipules convolute.
subsp. tenuissimus
1. Spike rarely interrupted; fruits olive to green-brown, 1.5–2.7 × 1.2–2.2 mm; keel 0.2 mm or more high; beak 0.2–0.6 mm; stipular veins decaying with age.
subsp. foliosus
1. Spike interrupted; fruits pale green, 1.4–1.7 × 1.1–1.2 mm; keel less than 0.2 mm high; beak 0.2 or less; stipular veins with age remaining as fibers
subsp. fibrillosus
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. pulcher, 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. 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
Subordinate taxa
P. pusillus subsp. gemmiparus, P. pusillus subsp. pusillus, P. pusillus subsp. tenuissimus
P. foliosus subsp. fibrillosus, P. foliosus subsp. foliosus
Name authority Linnaeus: Sp. Pl. 1: 127. 1753 (as pusillum) Rafinesque: Medical Repository hexade 2, 5:354. (1808)
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