Potamogeton friesii Rupr.
Family: Potamogetonaceae
Potamogeton friesii image

Perennial submersed aquatic herb 10 cm - 1 m tall Stem: sparsely branched below, slightly compressed, to 1 mm wide, jointed, often with paired nodal glands. Turions (small, over-wintering shoots) 1.5 - 5 cm long, with corrugate-based outer leaves and fan-shaped inner leaves set at right angles to the outer ones. Leaves: submersed, more or less arranged spirally, stalkless, translucent, light green, 2 - 7 cm long, 1 - 3 mm wide, linear with a slightly tapering base and pointed tip (with a short, tiny point), typically five- to seven-veined. Stipules axillary, free from leaf blade, white, rolled up, 0.5 - 2 cm long, becoming fibrous with age. Inflorescence: an upright, slender, cylindrical spike with two to five whorls of flowers, emersed, unbranched, 0.7 - 1.6 cm long, on a terminal or axillary stalk. Stalk flattened, slightly club-shaped, 1 - 5 cm long. Flowers: greenish, tiny. Stamens four. Anthers two-chambered, with four edge-to-edge sepal-like outgrowths. Fruit: an achene, stalkless, olive green to brown, 2 - 2.5 mm long, 1 - 2 mm wide, reverse egg-shaped with rounded sides, plump, not keeled, with an upright, 0.3 - 0.7 mm long beak.

Similar species: This species is easily identified by its turions (small, over-wintering shoots), which have corrugate-based outer leaves and fan-shaped inner leaves set at right angles to the outer ones.

Flowering: July to early August

Habitat and ecology: Occasional in lakes with clear water.

Occurence in the Chicago region: native


Etymology: Potamogeton comes from the Greek words potamos, meaning river, and geiton, meaning neighbor, referring to the habitat of these plants. Friesii is named after Elias Magnus Fries (1794-1878), a Swedish botanist.

Author: The Morton Arboretum

From Flora of Indiana (1940) by Charles C. Deam
In a few of our northern lakes.


Indiana Coefficient of Conservatism: C = 10

Wetland Indicator Status: OBL

Stem to 1 m or more, sparingly branched below, often more freely so above, slightly compressed, to 1 mm wide, commonly with paired glands at the nodes; rhizome scarcely developed; lvs all submersed, linear, 3-7 cm נ1.5-3 mm, minutely cuspidate at the obtuse or rounded tip, (3)5-7(9)-veined, the lateral veins very delicate, the midvein flanked by a row of lacunar cells on each side extending two-thirds its length, or these wanting; stipular sheaths axillary, free, white, 0.5-2 cm, closed at base when young, becoming fibrous in age; winter-buds commonly produced, 1.5- 5 cm, the inner lvs reduced and arranged into a fan-shaped structure, set at right angles to the outer lvs; peduncles 1.5-5 cm, flattened and clavate; spike slender, 8-18 mm, with 2-5 remote whorls of fls; frs ovoid to obovoid, 2-3 mm, with rounded sides, not or scarcely keeled; 2n=26. Chiefly in calcareous waters; Que. and Nf. to Mack. and Alas., s. to N.J., Pa., and Ind., n. Io., Nebr., and Utah.

