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Potamogeton praelongus


White-stem pondweed stem
White-stem pondweed stem

Habitat: White-stem pondweed grows in the submersed plant community of lakes and streams. This species is usually found in the colder, deeper portions of the littoral zone, in moderately fertile substrates.

Description: White-stem pondweed is an aquatic perennial with submersed leaves only. The leaves are large (8 to 30 cm long and 1 to 4 cm wide) and lance to oval shaped. The leaf margins fold toward each other at the tip, resembling the bow of a boat. When pressed to flatten, the tip appears notched. The leaves are alternately arranged, clasping to the stems at the base, with 3 to 5 strong veins and many weaker ones. The stems are pale green to whitish, slightly flattened, with a distinctive zig-zag appearance. Large, persistent, partially-fused stipules occur at the leaf axils. The flowers, followed by fruit, generally occur near the growing tips, and are densely arranged on cylindrical spikes. The small fruits are oval to egg shaped, with a prominent keel along a portion of the outer rim, ending in a blunt protrusion called a beak.

White-stem pondweed stem
White-stem pondweed is easily identified
by its large leaves with bow-like tips,
large persistens stipules, and zigzag stem

White-stem pondweed Range Map
U.S. range map of white-stem pondweed

U.S. Range: White-stem pondweed is native to Maine and New England and occurs throughout much of the northern and western United States. White-stem pondweed hybridizes with P. amplifolius and P. perfoliatus.

Annual Cycle: White-stem pondweed is an aquatic perennial that propagates from seeds and creeping rhizomes. Plants dieback to the rhizomes as winter sets in. New growth sprouts from rhizomes and seeds as the water warms in the spring. Flowers, followed by fruits, occur in mid summer.

Value to the Aquatic Community: The leaves of white-stem pondweed offer shade, shelter and foraging opportunities for fish. Fruits are a valuable food for waterfowl.

Look Alikes: May be confused with other species of the Potamogeton genus including curly-leaf pondweed.

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White-stem pondweed White-stem pondweed specimen White-stem pondweed range map White-stem pondweed illustration

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