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Hill's pondweed

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

Rhizomes

absent.

absent.

Cauline stems

slightly compressed, without spots, 30–60 cm;

glands rare, when present, brown to green, 0.1–0.3 mm diam.

terete, without spots, 27–95 cm;

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

Turions

terminal, rare, 2.8–3 cm × 1.5–3 mm, soft;

leaves ± 2-ranked;

outer leaves 3–4 per side, base not corrugate, apex acute to apiculate;

inner leaves undifferentiated.

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.

Leaves

submersed, ± spirally arranged, sessile, delicate;

stipules persistent, inconspicuous, convolute, free from blade, white to light brown, not ligulate, 0.7–1.6 cm, slightly fibrous, rarely shredding at tip, apex obtuse;

blade pale green to olive-green, linear, not arcuate, 2–6 cm × 0.6–2.5(–4) mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, apiculate to bristle-tipped or rarely blunt, lacunae in 1–2 rows each side of midrib;

veins 3.

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).

Inflorescences

unbranched, emersed;

peduncles not dimorphic, axillary and/or terminal, erect to ascending, rarely recurved, slightly clavate, 6–13.5 mm;

spikes not dimorphic, globose, (2–) 4–7 mm.

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.

Fruits

brown to light greenish brown, ovoid to orbicular, turgid, sessile, abaxially and laterally keeled (3-keeled), 2.3–4 × 2–3.2 mm, lateral keels without points;

beak erect, 0.3–0.7 mm;

sides without basal tubercles;

embryo with 1 full spiral.

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.

Chromosome number

unknownnot available.

2n

= 26.

Potamogeton hillii

Potamogeton strictifolius

Phenology Flowering and fruiting summer. Flowering and fruiting summer–fall.
Habitat Alkaline waters of marshes, ponds, lakes, and slow-moving streams Alkaline waters of lakes and slow-moving streams
Elevation 50–400 m (200–1300 ft) 50–2000 m (200–6600 ft)
Distribution
from FNA
CT; MA; MI; NY; OH; PA; VA; VT; WI; ON
[WildflowerSearch map]
[BONAP county map]
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]
Discussion

Potamogeton hillii is an easily recognized species either in fruit or when sterile. The leaf blade has a bristle tip and five or fewer veins. Those characters combined with the usual absence of nodal glands will separate this species from all other North American linear-leaved species. Ecologically, it is consistently found in more alkaline waters than any other North American pondweed. A study of 35 localities established the mean to be 124.1 mg/l CaCO3 (C. B. Hellquist 1984).

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

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.)

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. 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
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
Synonyms P. porteri P. strictifolius var. rutiloides
Name authority Morong: Botanical Gazette 6: 290, fig. 3. (1881) A. Bennett: J. Bot. 40: 148. (1902)
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