Potamogeton friesii
Potamogeton crispus
flat-stalk pondweed, Fries' pondweed, potamot de Fries
crisp-leaf pondweed, crispate leaf pondweed, curled pondweed, curly pondweed, curly-leaf pondweed, potamot crepu
absent.
absent.
compressed, without spots, 10–135 cm;
glands green, greenish brown, or gold, to 0.7 mm diam.
flattened, without spots, to 100 cm;
nodal glands absent.
terminal or lateral, common, 1.5–5 cm × 1.5–4 mm, soft;
leaves ± 4-ranked;
outer leaves 2–3 per side, base corrugate, apex apiculate to acute;
inner leaves reduced, arranged into fan-shaped structure and oriented at 90° angles to outer leaves.
common, axillary or terminal, 1.5–3 × ca. 2 cm, hard;
leaves ± 2-ranked;
outer leaves 1–4 per side, base not corrugate, apex rounded;
inner leaves rolled into linear, terete structure, oriented parallel to outer leaves.
submersed, ± spirally arranged, delicate to rigid, sessile;
stipules not persistent, inconspicuous, convolute, free from blade, white, not ligulate, 0.55–2.1 cm, fibrous, coarse, shredding at tip, apex obtuse;
blade light green, rarely olive-green to.somewhat reddish, linear, not arcuate, 2.3–6.5 cm × 1.2–3.2 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to apiculate, lacunae absent or 1 narrow row each side of midrib;
veins 5–7(–9).
submersed, ± spirally arranged, sessile, lax;
stipules persistent to deliquescent, inconspicuous, convolute, free from blade, brownish, not ligulate, to 0.5 cm, not fibrous, not shredding at tip, apex obtuse;
blade light to dark green, linear, not arcuate, 1.2–9 cm × 4–10 mm, base obtuse to rounded, without basal lobes, not clasping to nearly clasping, margins conspicuously serrate, not crispate, apex not hoodlike, round to round-acute, lacunae in 2–5 rows each side of midrib;
veins 3–5.
unbranched, emersed;
peduncles not dimorphic, terminal or axillary, erect or rarely recurved, slightly clavate, 1.2–4.1(–7) cm;
spike not dimorphic, cylindric, 7–16 mm.
unbranched, emersed;
peduncles not dimorphic, terminal or rarely axillary, erect to ascending, cylindric, 2.5–4 cm;
spikes not dimorphic, cylindric, 10–15 mm.
sessile, olive-green to brown, obovoid, turgid, not abaxially or laterally keeled, 1.8–2.5 × 1.2–2 mm;
beak erect, 0.3–0.7 mm;
sides without basal tubercles;
embryo with 1 full spiral.
sessile, red to reddish brown, obovoid, turgid to slightly concave, not abaxially or laterally keeled, 6 × 2.5 mm;
beak apically recurved, 2–3 mm;
sides without basal tubercles;
embryo with 1 full spiral.
= 26.
= 52 (Europe).
Potamogeton friesii
Potamogeton crispus
Potamogeton friesii is a fairly common linear-leaved species, especially of calcareous waters of lakes and streams of the upper Midwest. Whenever turions are present, the species is easily identified, as it is the only one with the outer leaves of the turions having corrugate bases and the inner leaves turned at right angles to the outer leaves.
Two hybrids, Potamogeton friesii × P. pusillus (= P. × pusilliformis Fischer [P. × intermedius Fischer]) and P. friesii × P. obtusifolius (= P. × semifructus A. Bennett ex Ascherson & Graebner), have been described.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
No specimens have been seen from New Brunswick, but the species is to be expected there.
Potamogeton crispus, an introduced species, has spread throughout much of North America. The expansion of this species’s range from its original collection in North America, apparently about 1840, has been discussed (R. L. Stuckey 1979). This is the only species of pondweeds in North America with serrate leaves and consequently it is easily recognized.
Life history of Potamogeton crispus is unusual as it flowers and fruits in late spring and early summer, at which time it also produces turions. The plants decay shortly after those structures develop, leaving only fruits and turions, which survive the summer. No one has observed any seed germination, but the turions (referred to as dormant apices) germinate in late summer or fall, and the plants overwinter as small plants only a few cm centimeters in size, even under the ice in northern climates (R. L. Stuckey et al. 1978). Growth then continues as the water begins warming in the spring.
One hybrid, Potamogeton crispus × P. praelongus (= P. × undulatus Wolfgang ex Schultes & Schultes f.), has been described.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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