Rhizomes absent. Cauline stems flattened, without spots, to 100 cm; nodal glands absent. Turions 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. Leaves 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. Inflorescences unbranched, emersed; peduncles not dimorphic, terminal or rarely axillary, erect to ascending, cylindric, 2.5--4 cm; spikes not dimorphic, cylindric, 10--15 mm. Fruits 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. 2n = 52 (Europe). Flowering spring--summer. Quiet waters, especially brackish, alkaline, or eutrophic waters of ponds, lakes, and streams; 0--2000 m; introduced; Alta., B.C., Ont., Que., Sask.; Ala., Ariz., Ark., Calif., Conn., Del., D.C., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Mo., Nebr., Nev., N.H., N.J., N.Y., N.C., Ohio, Okla., Oreg., Pa., R.I., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Central America (Costa Rica); South America (Colombia, and Argentina); Eurasia; Australia. 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.

Perennial submersed aquatic herb 30 cm - 1 m tall Stem: flattened, sparingly branched, jointed. Leaves: submersed, more or less arranged spirally, stalkless, translucent, 1.2 - 9 cm long, 4 - 12 mm wide, linear with a rounded base and rounded to nearly pointed tip, three- to five-veined, finely and irregularly toothed, wavy along the margins. Stipules free from leaf blade, brownish, rolled up, 3 - 5 mm long, scarious (dry, thin, and membranous). Inflorescence: an upright, dense, cylindrical spike of flowers, emersed, unbranched, 1 - 2 cm long, usually on a terminal stalk. Stalk cylindrical, 2 - 5 cm long. Flowers: greenish, tiny. Stamens four. Anthers two-chambered, with four edge-to-edge sepal-like outgrowths. Fruit: an achene, stalkless, reddish to reddish brown, to 3 mm long, reverse egg-shaped, plump to slightly concave, shallowly pitted, with an upright, 2 - 3 mm long beak.

Similar species: This species is easily distinguishable by its toothed leaves.

Flowering: late May to early September

Habitat and ecology: Introduced from Europe and now spread throughout much of North America. Increasingly common in lakes and ponds.

Occurence in the Chicago region: non-native

Notes: Plants in the genus Potamogeton are very important to wildlife, offering habitat and food for many aquatic animals.

Etymology: Potamogeton comes from the Greek words potamos, meaning river, and geiton, meaning neighbor, referring to the habitat of these plants. Crispus means "with wavy margins."

Author: The Morton Arboretum

From Flora of Indiana (1940) by Charles C. Deam

I have found this species in both Cedar Lake and Wolf Lake in Lake County. It was reported from Wolf Lake as early as 1913. In 1937 I found a few plants in shallow water on the south side of Lake Cicott, Cass County. Doubtless it is not common in this lake because a few years ago I spent a half day in a boat in search for pondweeds in this small lake and I did not find it.

……

Indiana Coefficient of Conservatism: C = null, non-native

Wetland Indicator Status: OBL

V Plants (Morton Arboretum), USDA GRIN, FNA, Heil et al 2013

Duration: Perennial Nativity: Non-Native Lifeform: Forb/Herb General: Perennial submersed aquatic herb; stems 30-100 cm long, flattened, sparingly branched, jointed. Leaves: Submersed, sessile, more or less arranged spirally; blades translucent, 1 - 9 cm long, 4 - 12 mm wide, linear with a rounded base and a rounded to nearly pointed tip, three- to five-veined, finely and irregularly toothed, wavy along the margins. Stipules free from leaf blade, brownish, rolled up, 3 - 5 mm long, scarious (dry, thin, and membranous). Flowers: Inflorescence a small, dense, cylindrical spike of flowers, upright and emergent from the water, 1 - 2 cm long, usually on a terminal stalk; stalk cylindrical, 2 - 5 cm long; flowers greenish, tiny; tepals 4; stamens 4; anthers two-chambered, with 4 edge-to-edge sepal-like outgrowths. Fruits: Sessile drupe, reddish to reddish brown, to 3 mm long, obovoid, keeled, with an upright, 2 - 3 mm long beak. Ecology: Found in lakes, ponds, rivers, and irrigation ditches, below 6,500 ft (1981 m); flowers May-September. Distribution: Native to Eurasia, Africa, and Australia. Introduced into North and South America. In North America, it is present throughout the lower 48 states, Mexico, and the southern Canadian provinces. Notes: 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 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. Ethnobotany: Unknown, but other species in the genus have uses. Etymology: Potamogeton comes from the Greek words potamos, meaning river, and geiton, meaning neighbor, referring to the habitat of these plants. Crispus means "with wavy margins." Editor: AHazelton 2015

Stems compressed, 3-8 dm, sparingly branched; rhizomes elongate and slender; lvs all submersed, linear-oblong, 3-8 cm נ5-12 mm, rounded or obtuse to minutely cuspidate, finely and irregularly toothed and rather crisply undulate-margined, narrowed or rounded to a sessile base, 3-5-veined; stipular sheaths 3-8 mm, adnate at base to the lf, scarious, soon disintegrating; hard winter-buds commonly produced; peduncles 2-5 cm, often recurved in fr; spike dense, 1-2 cm; body of the achene ovoid, 3 mm, shallowly pitted, with 3 round dorsal keels, the central one prolonged at base into a projecting appendage; achene-beak erect, conic, 2-2.5 mm; 2n=52. Native of Europe, locally intr. in alkaline or high-nutrient waters nearly throughout our range.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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