Potamogeton natans |
Potamogeton praelongus |
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broad-leaf pondweed, floating pondweed, floating-leaf pondweed, potamot flottat |
long-stalk pondweed, potamot à longs pédoncules, white-stalk pondweed, white-stem pondweed |
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Cauline stems | terete, often rust-spotted, 30–90 cm; nodal glands absent. |
terete, without spots, to 210 cm; nodal glands absent. |
Turions | absent. |
absent. |
Leaves | both submersed and floating, ± spirally arranged. |
submersed, ± spirally arranged, sessile, lax; stipules persistent, conspicuous, convolute, free from blade, white to green, not ligulate, 3–8.1 cm, fibrous, shredding at apex; blade pale green, rarely olive green, linear-lanceolate, not arcuate, 0.8–2.8 cm × 11–46 mm, base clasping, without basal lobes, margins entire, rarely crispate, apex hoodlike, splitting when pressed, obtuse, lacunae absent; veins 11–33. |
Floating leaves | 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. |
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Submersed leaves | 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. |
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Inflorescences | unbranched, emersed; peduncles not dimorphic, terminal, erect to ascending, cylindric, 4.5–9.5 cm; spikes not dimorphic, cylindric, 25–50 mm. |
emersed, unbranched; peduncles not dimorphic, terminal or axillary, erect to spreading, cylindric, 9.5–53 cm; spikes not dimorphic, cylindric, 34–75 mm. |
Fruits | 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. |
sessile, greenish brown, obovoid, turgid, abaxially keeled, occasionally laterally keeled, 4–5.7 × 3.2–4 mm, lateral keels when present without points; beak erect, 0.6–1 mm; sides without basal tubercles; embryo with 1 full spiral. |
Rhizome(s) | present. |
present. |
2n | = 52. |
= 52. |
Potamogeton natans |
Potamogeton praelongus |
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Phenology | Flowering summer–fall. | Flowering summer–fall. |
Habitat | Quiet or slow-flowing waters of ponds, lakes, and streams | Neutral to alkaline waters of lakes, rivers, and streams |
Elevation | 0–3100 m (0–10200 ft) | Greenland; 100–3000 m (Greenland; 300–9800 ft) |
Distribution |
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
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AK; CA; CO; CT; IA; ID; IN; MA; ME; MI; MN; MT; NE; NH; NJ; NY; OR; PA; SD; UT; VT; WI; WY; AB; BC; MB; NB; NF; NS; NT; NU; ON; PE; QC; SK; YT; Mexico; Greenland; Eurasia
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Discussion | 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.) |
Potamogeton praelongus is one of the easiest pondweeds to identify with its submersed leaves only clasping the more or less zigzagged stem. The persistent, hugelarge, white stipules provide another clue to this species. Four hybrids, Potamogeton perfoliatus × P. praelongus (= P. × cognatus Ascherson & Graebner), P. alpinus × P. praelongus (= P. × griffithii A. Bennett), P. crispus × P. praelongus (= P. × undulatus Wolfgang ex Schultes & Schultes f.), and P. gramineus × P. praelongus (= P. × vilnensis Galinus), have 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 | ||
Name authority | Linnaeus: Sp. Pl. 1: 126. (1753) | Wulfen: Arch. Bot. (Leipzig) 3: 331. (1805) |
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