• Don Yurewicz

Broad-Leaved Submerged Pondweeds

Updated: May 6, 2020

White Stem Pondweed (Potamogeton praelongus)

Photo by Jessica O'Brien University of California, Berkeley

White-stem pondweed is an aquatic perennial with submersed leaves only. The leaves are large (4-8 inches 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. (Excerpted from Wikipedia)

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

Clasping-Leaf Pondweed (Potamogeton perfoliatus)

Source: Lake Stewards of Maine

This pondweed grows from robust creeping perennial rhizome that produces round stems up to 10 ft long. The leaves are oval and translucent, with no stalk, 3/4 to – 4 1/2 inches long and 3/4 to – 1 1/2 inches wide, clasping the stem , a flat apex, and 5-12 veins on either side of the midrib. They vary considerably in color and may be bright green, dark green, yellowish, olive or brownish green. (Excepted from Wikipedia)

May be confused with other species of the Potamogeton genus including curly-leaf pondweed (exotic). Leaves on curly-leaf pondweed, however, do not clasp the stem as does this pondweed.

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