Potamogeton crispus

Curly-leaf Pondweed

CURLY-LEAVED PONDWEED

NOT NATIVE TO MAINE - INVASIVE

Habitat: Curly-leaf pondweed is found in the submersed plant community. Generally preferring soft sediments, it grows in waters that are shallow or deep, still or flowing. Curly-leaf thrives where many other aquatic plants do not, for example in waters that are shaded, disturbed, polluted or turbid.

Description: Curly-leaf pondweed is a submersed aquatic perennial with submersed leaves only. (Some pondweed species have two distinct leaf types: submersed leaves and floating leaves.) The slightly flattened stems emerge from slender rhizomes and sprouting turions, often branching profusely as they grow, giving the plants a busy appearance. Mature stems average 0.4 to 0.8 meters in length. The leaves of this plant are key to its identification. Though the leaves share some characteristics with some native pondweeds, they also have three distinct characteristics that, together, set this plant apart from any of its native look alikes.

Stipules when visible (they disintegrate early) are slightly joined to the stem at the base and 4 to 10 mm long. Flower spikes appear above the surface of the water from June through September. The small flowers are arranged in a terminal spike on a curved stalk measuring about 7 cm in length. The fruits (seeds) have a prominent cone shaped beak and a bumpy ridge along the “crown.” (The shape resembles the profile of a crested woodpecker!) Turions form in the leaf axils during the growing season. The turions, resembling small ruffled pinecones, are hard (like stiff plastic) and typically 1 to 2 cm long.

Origin and Range: Curly-leaf pondweed is native to Eurasia. Introduced to the US some time during the mid 1800s, it has since spread to almost every state in the country. In addition to spread by natural causes and recreational activity, curly leaf has been planted intentionally for waterfowl and wildlife habitat, and possibly has been spread as a contaminant in water used to transport fishes and fish eggs to hatcheries. Curly-leaf was first confirmed in a small pond in southern Maine in 2004 and is currently present in the nearby states of New Hampshire, Massachusetts, Vermont, Connecticut, New York and Rhode Island.

Annual Cycle: Curly-leaf pondweed is adapted to grow in cool conditions, sprouting from rhizomes and turions in the late fall and through the winter, and reaching maturity relatively early in the season (late spring through early summer). Flowers and turions are produced during the growing season and the plants generally begin breaking up as early as mid-July. The turions scatter with the plant fragments and drop to the sediments, where they lie dormant until the water begins to cool again in the fall.

In addition to propagation by turion and creeping rhizomes, curly-leaf pondweed produces seeds. The importance of seeds, however, in the spread and propagation of this plant remains unknown.

Impacts: Curly-leaf pondweed is a highly competitive plant, capable of rapid growth and spread. Infestations may displace native species, reduce biodiversity, impede recreational activities, and reduce property values. As the dense mats of vegetation decay, available oxygen in the water may be depleted. The resulting anoxic (low oxygen) conditions may lead to fish kills and harm other aquatic organisms. Nutrients released from the decaying plant matter may also contribute to cultural eutrophication and algae blooms.

Look Alikes: May be confused with large-leaf pondweed, clasping-leaf pondweed, and other species within the Potamogeton genus.