Don't Let It Loose! - Eurasian Watermilfoil

Don’t Let It Loose! - Eurasian watermilfoil, Myriophyllum spicatum

Where does the species originate from?

Eurasian watermilfoil originates from Europe and Asia.

How is it introduced and spread?

Milfoil was once commonly sold as an aquarium plant. Now it is largely spread through escapes or releases from ornamental ponds, boat trailers moving between waterbodies, and subsequent natural dispersal. Wildlife, water currents and flood events can all carry small fragments of the plant to new places where it can reproduce vegetatively. This means it only takes a small stem or plant fragment to start new colonies in waterbodies where it is introduced.

Environmental impact:

This aquatic plant grows in dense patches, excluding light from native species and creates stagnant areas with low oxygen levels below the large floating mats. Recreational activities such as fishing, swimming and boating are greatly impaired where thick mats occur. 

Milfoil facts:

·       Milfoil can grow up to 2 inches per day.

·       A single fragment of stem or leaves can begin a new milfoil infestation.

·       Eurasian milfoil has been spread by earthworm farmers who packed their product in the aquatic plant for transport.

Don’t Let It Loose!  Even though Eurasian watermilfoil forms dense infestations in 43 states, it has not yet been added to the U.S. Federal Noxious Weed List and continues to be sold through aquarium supply dealers and over the Internet. Only you can prevent its spread! Clean, Drain, and Dry your boat and equipment after recreating in your favorite lake or waterbody.

Submitted by Briita Orwick, Aquatic Invasive Species Intern, Pacific Region