The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links
Photo is of parent taxon

fibrous pondweed

closed-leaf pondweed, leafy pondweed

Rhizomes

absent.

Stems

glands common, to 0.5 mm diam.

Cauline stems

slightly compressed, without spots, 4–75 cm;

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

Turions

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

stipules brown or rarely white, fibrous, shredding at tip, veins in age remaining as fibers.

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

spikes interrupted.

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

pale -green, 1.4–1.7 × 1.1–1.2 mm;

keel less than or equal to 0.2 mm high;

beak less than or equal to 0.2 mm.

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.

Chromosome number

unknownnot available.

Potamogeton foliosus subsp. fibrillosus

Potamogeton foliosus

Phenology Flowering and fruiting summer–fall.
Habitat Warm waters of shallow lakes, springs, streams, and rivers
Elevation 600–2700 m (2000–8900 ft)
Distribution
from FNA
CA; ID; OR; UT; WA; WY
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

Potammogeton foliosus subsp. fibrillosus is known from the warm waters of the northwestern United States. It differs from subsp. foliosus by the stipular tissue between the veins decomposing, leaving only strands formed by the fibrous veins. In addition, nodal glands are quite common.

Of conservation concern.

(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. 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 > Potamogeton foliosus Potamogetonaceae > Potamogeton
Sibling taxa
P. foliosus subsp. foliosus
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. foliosus subsp. fibrillosus, P. foliosus subsp. foliosus
Synonyms P. fibrillosus, P. foliosus var. fibrillosus
Name authority (Fernald) R. R. Haynes & Hellquist: Novon 6: 370. (1996) Rafinesque: Medical Repository hexade 2, 5:354. (1808)
Web links