The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links

northern snail-seed pondweed, potamot spirille, spiral pondweed

broad-leaf pondweed, floating pondweed, floating-leaf pondweed, potamot flottat

Rhizomes

present.

present.

Cauline stems

compressed, without spots, 5–40 cm;

glands absent.

terete, often rust-spotted, 30–90 cm;

nodal glands absent.

Turions

absent.

absent.

Leaves

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

both submersed and floating, ± spirally arranged.

Floating leaves

petiolate;

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

blade adaxially light green, oblong to obovate, 0.7–—3.5 cm × 2–13 mm, base tapered to rounded, apex obtuse, rounded;

veins 5–15.

petioles lighter green immediately proximal to apex, 5.5–29 cm;

blade adaxially light green, elliptic to ovate, 3.5–11 cm × 15–60 mm, base cordate, apex acute to rounded;

veins 17–37.

Submersed leaves

sessile, lax;

stipules persistent to deliquescent, inconspicuous, convolute, adnate to blade for ½ stipule length, reddish brown to light green, ligulate, 2–12 mm, not fibrous, not shredding at tip, apex obtuse;

blade red-brown to light green, linear, not arcuate, 0.8–8 cm × 0.5–2 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, obtuse to acute, lacunae present, a broad band each side of midvein;

veins 1–3.

sessile, rigid;

stipules persistent, conspicuous, convolute, free from blade, whitish, not ligulate, 4.5–1 cm, fibrous, not shredding at tip, apex obtuse;

blade light to dark green, phyllodial, not arcuate, 9–20 cm × 0.7–2.5 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, obtuse, lacunae absent;

veins 3–5, obscure.

Inflorescences

unbranched;

peduncles dimorphic, submersed axillary, recurved, clavate, 0.5–3 mm, emersed axillary or terminal, erect to recurved, slightly clavate, 4–27 mm;

spikes dimorphic, submersed capitate, 2–5 mm, emersed ellipsoid to cylindric, 4–13 mm.

unbranched, emersed;

peduncles not dimorphic, terminal, erect to ascending, cylindric, 4.5–9.5 cm;

spikes not dimorphic, cylindric, 25–50 mm.

Fruits

sessile, greenish brown, somewhat orbicular, compressed, abaxially winged, laterally winged, 4–13 × 1.3–2.4 mm, lateral wing with blunt tips;

beak absent;

sides without basal tubercles;

embryo with more than 1 full spiral.

sessile, green to greenish brown, obovoid, turgid, not abaxially or laterally keeled, 3.5–5 × 2–3 mm;

beak erect to apically recurved, 0.4–0.8 mm;

sides without basal tubercles;

embryo with 1 full spiral.

2n

= 52.

Potamogeton spirillus

Potamogeton natans

Phenology Flowering mid summer–late fall. Flowering summer–fall.
Habitat Neutral to acidic waters of ponds, lakes, and streams Quiet or slow-flowing waters of ponds, lakes, and streams
Elevation 0–400 m (0–1300 ft) 0–3100 m (0–10200 ft)
Distribution
from FNA
CT; IA; MA; ME; MI; MN; NE; NH; NJ; NY; OH; PA; RI; VT; WI; MB; NB; NF; NS; ON; PE; QC
[WildflowerSearch map]
[BONAP county map]
from FNA
AK; AZ; CA; CO; CT; IA; ID; IL; IN; KS; MA; ME; MI; MN; MT; ND; NE; NH; NJ; NM; NV; NY; OH; OR; PA; RI; SD; UT; VT; WA; WI; WV; WY; AB; BC; MB; NB; NF; NS; NT; ON; PE; QC; SK; YT; Eurasia
[WildflowerSearch map]
[BONAP county map]
Discussion

The This is the firstone of three Potamogeton species in the flora area with dimorphic inflorescences. It can be separated from the other two species because its submersed leaf blades have broad lacunae, extending nearly from the midvein to the margin, and its fruits have lateral wings with blunt points along it. along them.

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

Potamogeton natans is the common floating-leaved pondweed of the north temperate ure areas. It is essentially circumboreal and can easily be identified by floating leaves that are almost always cordate at the base of the blade, the petiole with a short band of light tissue at its apex, and the submersed phyllodial leaves. Also, the apex of the petiole usually is bent so that the blade appears oriented in the opposite direction from which the petiole appears to be oriented.

One hybrid, Potamogeton natans × P. nodosus (= P. × schreberi Fischer [P. × perplexus A. Bennett]), has 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. praelongus, P. pulcher, P. pusillus, P. richardsonii, P. robbinsii, 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. 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
Name authority Tuckerman: American Journal of Science, and Arts ser. 2, 6:228. (1848) Linnaeus: Sp. Pl. 1: 126. (1753)
Web links