NATIVE TO MAINE
Description: Large-leaf pondweed is a large, stately plant, with two distinct leaf types. The submersed leaves (3 to 7 cm wide) are the broadest of any pondweed in Maine. The many veins of these supple, translucent leaves are easy to see when held to the light. The leaves are often gracefully arched, with the outer margins folding slightly toward one another at the midvein. They are alternately arranged on robust stems, attached by leaf stalks that vary in length from 1 to 6 cm. The floating leaves are slightly smaller (2.5 to 5 cm wide), more oval-shaped, and not translucent. They generally occur in opposite pairs at the top of the plant, also attached to the stem by leaf stalks. The stalks of the floating leaves are generally quite long (up to 30 cm). The stipules of both leaf types are large (3.5 – 12 cm long), largely free from the stem, and tapering to a sharp point. The flowers, followed by fruit, occur among the floating leaves and are densely arranged on an emergent spike. The individual fruits are oval to egg-shaped with a small beak protruding from a point along the outer rim.
US Range: Large-leaf pondweed is native to Maine, New England and much of the United States.
Annual Cycle: Large-leaf pondweed is an aquatic perennial that propagates by seed and spreading rhizome. Plants may overwinter intact, but winter die-back to the rhizome is common. In the spring the rhizomes sprout, flowers appear by midsummer and fruit matures by late summer.
Value to the Aquatic Community: The broad leaves of P. amplifolius offer shade, shelter and foraging opportunities for fish. Fruits are produced in abundance and 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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Water Quality Monitoring
Aquatic Invasive Monitoring
Maine Volunteer Lake Monitoring Program
24 Maple Hill Road, Auburn, ME 04210
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