Potamogeton epihydrus
Potamogeton crispus
Nuttall's ribbon-leaf pondweed, potamot emerge, ribbon-leaf pondweed
crisp-leaf pondweed, crispate leaf pondweed, curled pondweed, curly pondweed, curly-leaf pondweed, potamot crepu
present.
absent.
flattened, without spots, 10–90 cm;
glands absent.
flattened, without spots, to 100 cm;
nodal glands absent.
absent.
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.
both submersed and floating or floating absent, ± spirally arranged.
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.
petiolate;
petioles continuous in color to apex, 2–12.5 cm;
blade adaxially light green, narrowly oblong-oblanceolate to elliptic, 2–8 cm × 4–20 mm, base acute, apex rounded or bluntly cuspidate;
veins 11–41.
sessile, lax;
stipules persistent, inconspicuous, convolute, free from blade, red-brown, not ligulate, 1–3 cm, not fibrous, not shredding at tip, apex obtuse;
blade red-brown to light green, linear, not arcuate, 5–22 cm × 1–10 mm, base not clasping, without basal lobes, margins entire, not crispate, apex not hoodlike, blunt to acute, lacunae present, broad band each side of midvein;
veins 3–13.
unbranched, emersed;
peduncles not dimorphic, axillary, erect, cylindric, 1.5–5(–16) cm;
spikes not dimorphic, cylindric, 0.8–4 cm.
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, greenish brown, round-obovoid, flattened, abaxially and laterally keeled, 2.5–4.5 × 2–3.6 mm, lateral keels without sharp points;
beak erect, 0.5 mm;
sides without basal tubercles;
embryo with less than 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 epihydrus
Potamogeton crispus
No specimens have been seen from Maryland, but the species is to be expected there.
Two varieties, Potamogeton epihydrus var. epihydrus and var. ramosus, have been recognized. These prove not to be distinct. Both varieties often grow in the same body of water in the same population. The wider-leaved plants often occur in more alkaline waters. Two hybrids, P. epihydrus var. nuttallii × P. gramineus and P. epihydrus × P. nodosus (= P. ×subsessilis Hagström), have been described.
Potamogeton epihydrus is a common species of lakes and streams of northern United States and southern Canada. It extends southward in the eastern United States to Louisiana and Alabama. Potamogeton epihydrus is one of our more easily recognized species: it has floating leaves, linear submersed leaves, and fruits with an embryo with one full spiral or less. The only other North American pondweed with a similar set of characteristics is P. tennesseensis, which differs from P. epihydrus by the former having long tapering apices in the submersed leaves whereas the latter has blunt to acute apices.
(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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