Curly Pondweed, Curly Leaf Pondweed
General: Herbaceous, partially, or entirely submersed aquatic species; some leaves may float on the surface.
Flowers: Curled Pondweed has small and reddish-brown flowers, with 4 petal-like lobes, and are arranged in a dense spike on a curved 2.5 – 5 cm stalk. Flower spikes often emerge above the water surface.
Stem: The Curled Pondweed stems are light green or yellowish-white, branched, and flattened. Stems can be 1 m or longer in deeper waters. Turions (bur-like, prickly buds that form at or near peak biomass) form along the stem just above the site of leaf attachment.
Leaves: Curled Pondweed leaves are lance-shaped, somewhat translucent and appear reddish-green when submerged but light to dark green when out of the water. Leaves are 0.5 – 1.5 cm wide to 3 – 10 cm long, wavy, and arranged in a spiral along the stem.
Large-leaved Pondweed (Potamogeton amplifolius) has leaves with smooth edges.
Habitat and Origin
Curled Pondweed is native to Eurasia, Africa, and Australia. It was first introduced to the US in the mid-1800s through fish stocking operations, likely by accident.
It is generally found in ponds, rivers, lakes, wetlands, streams, and brackish waters. Curled Pondweed prefers alkaline and eutrophic waters, and can be found in disturbed sites and polluted waters. It grows in waters 1 – 3 m deep in a range of sedimentary conditions, like gravel, fine sand, loamy mud, and clay.
Propagation & Vectors of Spread
Curled Pondweed reproduces mainly vegetatively, via rhizomatic spread. However, vegetative reproduction is also accomplished by plant fragments that can form whole new plants, as well as turions, which are bur-like, prickly buds that form along the stem at or near peak biomass. Turions are dispersed by water flow and can stay viable for up to 2 years. They eventually sink to the bottom of the waterbody and germinate the following year. Curled Pondweed can also reproduce by seed, but it has a very low germination rate.
Curled Pondweed fragments and turions are transported by boats and other pieces of aquatic equipment. Turions are also dispersed by wind and water flow. Waterfowl can spread the plant great distances along their migratory routes. Curled Pondweed is also spread by humans, as it is often accidentally included in aquaculture mailings.
Ecological, Economic, & Health Impacts
- Outcompetes native aquatic vegetation by limiting the light available for photosynthesis.
- Can cause algal blooms and ultimately eutrophication in water bodies, which may result in the death of fish and other aquatic species due to hypoxic conditions.
- Decreases the real estate value and the aesthetic appeal of a waterbody.
- Negatively impacts tourism by impeding recreational activities such as boating, fishing, and swimming.
What Can I Do?
Curled Pondweed is currently found in Whistler, but not Squamish or Pemberton, so the best approach to controlling its spread is by PREVENTION.
Learn to identify Curled Pondweed: use the images presented in this profile page to learn how to identify Curled Pondweed.
What to do if you spot it: You can report any Curled Pondweed sighting by clicking here.
- Ensure that plants are disposed of in a garbage bag if found in floral arrangements to prevent seeds from spreading.
- Clean, Drain, and Dry all watercraft. Rinse all mud, debris, and plant fragments from all equipment, wading gear, and boats.
- Do not plant Curled Pondweed in a water garden.
- Do not dispose of aquarium plants into water bodies.
Benthic barriers made from a variety of materials can be placed over an infestation to prevent sunlight from reaching the plants and restrict upward growth. Installation should occur during spring to prevent the plants from exceeding 0.5 m tall and greatly increasing their biomass.
However, keep in mind that benthic barriers affect all vegetation, not just the undesirable Curled Pondweed.
Raking and hand-cutting Curled Pondweed is a relatively effective method of mechanical control but should be performed early in the season. Ensure that as many plant fragments are removed as possible, as any left could produce new plants. Cutting at the sediment surface has been shown to reduce turion production.
Mechanical methods generally need to be repeated for several years, and monitored thereafter to ensure the plant doesn’t re-establish.
Herbicides cannot be applied in aquatic environments in Canada. Herbicide control is not recommended for this species.
Sterile triploids of the White Amur Grass Carp (Ctenopharyngodon idella) can be used to control Curled Pondweed infestations, as they are a relatively non-selective herbivorous species. Careful monitoring of feeding impacts is necessary, as the fish might also consume desirable aquatic vegetation.
- Adirondack Water Institute, Curly-leaf Pondweed (Potamogeton crispus), https://www.adkwatershed.org/stewardship/invasive-species-info/curly-leaf-pondweed
- Electronic Atlas of the Flora of BC, Noxious and Problem Plants of British Columbia, https://ibis.geog.ubc.ca/biodiversity/eflora/Invasive_Species_Checklist_2012.pdf
- Fraser Valley Invasive Species Society, Curly-leaf Pondweed, https://www.fviss.ca/invasive-plant/curly-pondweed
- Global Invasive Species Database, Potamogeton crispus, http://www.iucngisd.org/gisd/species.php?sc=447
- Illinois Wildflowers, Curly Pondweed, https://www.illinoiswildflowers.info/wetland/plants/curly_pondweed.html#:~:text=In%20many%20areas%20of%20North,can%20displace%20native%20aquatic%20plants.&text=Range%20%26%20Habitat%3A%20Curly%20Pondweed%20is,where%20it%20is%20not%20native.
- Invasive Species Compendium, Potamogeton crispus (curlyleaf pondweed), https://www.cabidigitallibrary.org/doi/10.1079/cabicompendium.43664
- Invasive Species Council of Alberta, Curly Leaf Pondweed, https://abinvasives.ca/wp-content/uploads/2020/07/FDIP_FS-CurlyLeafPondweed.pdf
- Invasive Species Council of Manitoba, Curly Leaf Pondweed Factsheet, https://invasivespeciesmanitoba.com/site/uploads/pdf/Other%20Information/fs_pondweed.pdf
- Montana Field Guides, Curly-leaf Pondweed (Potamogeton crispus), https://fieldguide.mt.gov/speciesDetail.aspx?elcode=PMPOT03060
- Pennsylvania Sea Grant, Curly-leaf pondweed (Potamogeton crispus), https://seagrant.psu.edu/sites/default/files/CLP2013_reduced_0.pdf
- State of Michigan, Status and Strategy for Curly-leafed Pondweed (Potamogeton crispus L.), https://www.michigan.gov/documents/invasives/egle-ais-potamogeton-crispus_708948_7.pdf
- UC Davis, Curlyleaf Pondweed, https://tahoe.ucdavis.edu/curly-leaf-pondweed
- US Department of Agriculture National Invasive Species Information Center, Curly Pondweed, https://www.invasivespeciesinfo.gov/profile/curly-pondweed
- US Fish & Wildlife, Ecological risk screening summary – Curly Leaf Pondweed (Potamogeton crispus) – High risk, https://fws.gov/media/ecological-risk-screening-summary-curly-leaved-pondweed-potamogeton-crispus-high-risk
- Wisconsin Sea Grant, Curlyleaf Pondweed, https://www.seagrant.wisc.edu/our-work/focus-areas/ais/invasive-species/invasive-species-fact-sheets/plants/curlyleaf-pondweed/