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narrowleaf pondweed, potamot à feuilles raides, stiff-leaf pondweed, straight-leaf pondweed

potamot de Vasey, Vasey's pondweed

Rhizomes

absent.

absent.

Cauline stems

terete, without spots, 27–95 cm;

glands white, green, greenish brown, or gold, to 0.3 mm diam.

terete, without spots, 2–5 cm;

glands absent.

Turions

terminal or lateral, common, 2.5–4.8 cm × 0.8–2.2 mm, soft;

leaves ± 2-ranked, flattened with outer and inner leaves in same plane;

outer leaves 3–4 per side, base not corrugate, or rarely corrugate, apex acute;

inner leaves undifferentiated.

common, axillary, 0.5–2 cm × 0.5–1.2 mm, soft;

leaves ± 2-ranked;

outer leaves 2–3 per side, base not corrugate, apex acute;

inner leaves undifferentiated or rolled into tight, hardened structure.

Leaves

submersed, ± spirally arranged, rigid, sessile;

stipules disintegrating, inconspicuous, connate, free from blade, white, not ligulate, 0.6–1.6 cm, fibrous, shredding at tip, apex obtuse;

blade green to olive-green, linear, not arcuate, 1.2–6.3 cm × 0.6–2 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to nearly bristle-tipped, rarely obtuse to apiculate, lacunae absent;

veins 3–5(–7).

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

Floating leaves

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

blade adaxially greenish brown, elliptic, spatulate, or obovate, 0.6–1.5 cm × 3–8 mm, base acute, apex obtuse;

veins 5–9.

Submersed leaves

sessile, delicate;

stipules persistent, inconspicuous, convolute, free from blade, green to brown, not ligulate, 0.4–1.2 cm, not fibrous, not shredding at tip, apex attenuate;

blade light green, linear-filiform, not arcuate, 2–8 cm × 0.1–1 mm, bases slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to almost bristle-tipped, lacunae present, rarely absent, 0–2 rows each side of midvein;

veins 1(–3).

Inflorescences

unbranched, emersed;

peduncles not dimorphic, terminal, erect, rarely recurved, cylindric, rarely slightly clavate, 1–4.5 cm;

spike not dimorphic, cylindric, 0.6–1.3 cm.

unbranched, emersed;

peduncles not dimorphic, terminal, ascending in flower, recurved in fruit, cylindric, 5–30 mm;

spikes not dimorphic, cylindric or moniliform, 6–8 mm.

Fruits

sessile, green-brown, ovoid, turgid, not abaxially or laterally keeled, 1.9–2.1 × 1.3–1.8 mm;

beak erect, 0.5–0.8 mm;

sides without basal tubercles;

embryo with 1 full spiral.

sessile, green to brown, obliquely round-obovoid, compressed, abaxially keeled, not laterally keeled, 1.5–2.5 × 1.2–1.6 mm;

beak erect, 0.3–0.5 mm;

sides without basal tubercles;

embryo with 1 full spiral.

2n

= 26.

= 28.

Potamogeton strictifolius

Potamogeton vaseyi

Phenology Flowering and fruiting summer–fall. Flowering and fruiting summer–fall.
Habitat Alkaline waters of lakes and slow-moving streams Quiet waters of lakes, ponds, and rivers
Elevation 50–2000 m (200–6600 ft) 50–500 m (200–1600 ft)
Distribution
from FNA
CT; IL; IN; MA; ME; MI; MN; ND; NE; NY; OH; PA; SD; UT; VA; VT; WI; WY; AB; MB; NB; ON; QC; SK; YT
[WildflowerSearch map]
[BONAP county map]
from FNA
CT; IA; IL; IN; MA; ME; MI; MN; NH; NJ; NY; OH; PA; RI; VT; WI; NB; ON; QC
[WildflowerSearch map]
[BONAP county map]
Discussion

Potamogeton strictifolius is a relatively uncommon species found in alkaline waters. Fairly rigid leaves of the species make floating onto paper unnecessary in the collecting process. The leaves have a tendency to become revolute during the growing season. The species superficially resembles several other species of linear-leaved pondweeds. Consequently, many specimens of this species have been misidentified as other species and vice versa. Thus, literature records are often suspect.

One hybrid, Potamogeton strictifolius × P. zosteriformis (= P. × haynesii Hellquist & G. E. Crow), has been described.

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

All of the original material of Potamogeton lateralis Morong, including the collection designated as the lectotype, has been studied (C. B. Hellquist et al. 1988). Every specimen, was a mixed collection of P. pusillus and P. vaseyi. Based on the results of the study, P. lateralis is taxonomically nomenclaturally invalid and should be rejected.

Potamogeton vaseyi is an uncommon species that has submersed leaves very similar to P. pusillus subsp. gemmiparus. Floating leaves apparently are present only when the species is fertile, and the species often grows intermixed with that subspecies. Collections are consequently often a mixture of the two taxa. Also, sterile collections of either taxon can easily be mistaken for the other.

(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. spirillus, 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. 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. zosteriformis
Synonyms P. strictifolius var. rutiloides
Name authority A. Bennett: J. Bot. 40: 148. (1902) J. W. Robbins: in A. Gray, Manual of Botany of the Northern United States (ed. 5) 485. (1867)
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