Curly-Leaf Pondweed

Common Name: Curly-Leaf Pondweed
Other Names: Curled-Leaf Pondweed
Scientific Name: Potamogeton crispus

Curly-leaf pondweed (Potamogeton crispus) is a perennial, submerged aquatic plant that is native to Eurasia. It tolerates fresh or slightly brackish water and can grow in shallow, deep, still, or flowing water. It generally grows in 3-10 feet of water. Curly-leaf tolerates low water clarity and will readily invade disturbed areas. 

The origins of its introduction are unknown, but it is suspected that it was possibly imported as an aquarium ornamental or introduced accidentally with fish stocking operations during the late 1800's.


Identification:

• Leaves: All submersed and alternate with no leaf stalks; oblong, still, translucent leaves (4-10 cm long, 5-10 mm wide) have distinctly wavy edges with fine teeth and 3 main veins. Sheaths (stipules) up to 1 cm long are free of the leaf base and disintegrate with age.
  
  
• Flowers: Tiny, with 4 petal-like lobes; in spikes 1-3 cm long on stalks up to 7 cm long. 
  
  
• Fruits & Seeds: Seed-like achene (4-6mm long including 2-3 mm beak, back ridged). 
  
  
• Roots: Fibrous, from slender rhizomes. 
  
  
• Similar species: There are many pondweed species that are native Michigan, so careful identification is key to ensure proper treatment of only the invasive species. 

Photo Credit: Chris Evans, River to River CWMA, Bugwood.org

Diagram or Graphic; USDA NRCS. Wetland flora: Field office illustrated guide to plant species. USDA Natural Resources Conservation Service.

Photo Credit: Chris Evans, River to River CWMA, Bugwood.org

Ecological threat:

• Invades freshwater lakes, ponds, rivers, streams, and in slightly brackish waters. Can become dominant and invasive due to its tolerance for low light and low water temperatures. 
  
  
• May outcompete other underwater plants and become dominant, which causes problems due to the formation of dense mats that interfere with recreational activities. 
  
  
• Also causes an increase in phosphorus concentrations, causing an increase in algae blooms and a pile up of dying Curly-leaf pondweed along the shore.