Flora of North America species comparison

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Potamogeton richardsonii

clasping-leaf pondweed, potamot de Richardson, Richardson's pondweed
Cauline stems

terete, without spots, to 100 cm;

nodal glands absent.
Turions

absent.
Leaves

submersed, ± spirally arranged, sessile, lax;

stipules persistent, conspicuous, convolute, free from blade, white, not ligulate, 0.12–0.17 cm, fibrous, disintegrating to persistent fibers, even on proximal portion of stem, shredding at apex, apex obtuse;

blade olive green, ovate-lanceolate to narrowly lanceolate, not arcuate, 1.6–13 cm × 5–28 mm, base rounded, without basal lobes, clasping, margins entire to crispate, apex not hoodlike, not splitting when pressed, acute to obtuse, lacunae absent;

veins 3–35.
Inflorescences

emersed, unbranched;

peduncles not dimorphic, terminal or axillary, erect to rarely recurved, clavate, 1.5–14.8 cm;

spikes not dimorphic, cylindric, 13–37 mm.
Fruits

sessile, greenish brown, obovoid, turgid to concave, not or rarely abaxially keeled, not laterally keeled, 2.2–4.2 × 1.7–2.9 mm;

beak erect, 0.4–0.7 mm;

sides without basal tubercles;

embryo with 1 full spiral.
Rhizome

present.
2n

= 52.

Potamogeton richardsonii
Phenology Flowering summer–fall.
Habitat Alkaline waters of lakes, streams, and rivers
Elevation 0–3000 m (0–9800 ft)
Distribution
from FNA
AK; CA; CO; CT; IA; ID; IL; IN; MA; ME; MI; MN; MT; ND; NE; NH; NV; NY; OH; OR; PA; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NS; NT; ON; QC; SK; YT
[WildflowerSearch map]
[BONAP county map]
Discussion

Potamogeton richardsonii is quite similar to P. perfoliatus. Specific characteristics to separate the two species are the shape of the leaf blade apex, acute in P. richardsonii and obtuse in P. perfoliatus, and the condition of the stipules, disintegrating between the veins leaving fibrous strands in P. richardsonii, and the entire stipule, including the veins, disintegrating in P. perfoliatus.

Two hybrids, Potamogeton gramineus × P. richardsonii (= P. × hagstroemii A. Bennett [as hagstromii]) and P. nodosus × P. richardsonii (= P. × rectifolius A. Bennett), have been described.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 22.
Parent taxa 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. robbinsii, P. spirillus, P. strictifolius, P. subsibiricus, P. tennesseensis, P. vaseyi, P. zosteriformis
Synonyms P. perfoliatus var. richardsonii, P. perfoliatus subsp. richardsonii
Name authority (A. Bennett) Rydberg: Bulletin of the Torrey Botanical Club 32: 599. (1905)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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