Curly Leaf Pondweed (Potamogeton crispus)
Curly leaf pondweed is a submerged aquatic macrophyte. It's leaves are oblong and attached directly to the stem in an alternate pattern. The leaf margins of P. crispus are wavy, resembling a lasagna noodle or piece of bacon, and have fine teeth all along the leaf margins. When submerged, the plant appears reddish-brown, but when removed from the water it's green color becomes apparent. In spring, the plant will produce an emergent 1-2 inch flowering structure that bears small petaled flowers. By mid summer P. crispus will begin to produce winter buds, called turions. These vegetative winter buds, which remeble small pinecones, are an important reproductive agent for this plant. Studies have shown that lakes with curly leaf pondweed beds may contain up to 1600 turions in one sqaure yard. With a high germination rate of 60-80%, turions play a large role in the invasive nature of curly leaf pondweed.
Native range and Distribution
Native to Eurasia, curly leaf pondweed is now a cosmopolitan species with a worldwide distribution in Africa, Australia, and North America. Exactly when it was first presented to the United States is unknown, but the most agreed upon time is during the mid-1800s. The original means of introduction is also unidentified, but escapement from horticultures seems to be the most plausible culprit. Since the 1840s, when the earliest verifiable wild collection of P. crispus was found in waters around the Philadelphia, PA area, it has spread throughout the Northeastern United States within a few decades (Stuckey, 1979). Curly leaf pondweed is now found in nearly all 50 States and as far north as Calgary, Canada. It infests waters throughout the Great Lakes basin and the state of New York. In the Adirondack Park curly leaf pondweed has been identified in Lower Saranac Lake, Lake Flower, and Paradox Lake of Franklin and Essex counties as well as other water bodies.
Threat and impacts
Depending on the growth and establishment, curly leaf pondweed can have deleterious or advantageous effects on the economy and ecosystem. During the early spring-summer growths, the plants can form dense monocultures which can cover large areas of the water surface. These dense, pernicious growths can impede water flow in irrigation canals and restrict water based recreation. A lake in northern Tennessee had experienced such growths during sport fishing's peak time which severely hindered the season and related economy. Due to curly leaf pondweed's jumpstart on the season, it can crowd out other native aquatic plants. Even after P. crispus's summer die back, the crowded native plants do not show signs of recovery. The dieback also increases the nutrient load in the water column which subsequently can lead to harmful algae blooms and oxygen depleted water.
Since curly leaf pondweed can form pestiferous growths that distress the ecosystem and the economy, management methods have been implemented and include:
- Chemical herbicides - the most common management practice. The type of herbicide and time of treatment are important to consider for the greatest effect on reducing biomass and turion formation. Application is best conducted during the lowest point of carbohydrate storage (January and April) when the plant is most vulnerable to management and turion development has not yet occurred.
- Biological - Utilizing Triploid grass carp (Ctenopharyngodon idella) to graze on nusiance vegetation. Grass carp have been shown to have a preference for curly leaf pondweed above other aquatic plants.