Eurasian Watermilfoil
(Myriophyllum spicatum)
Biological Category
Plants
NY Legal Status
Prohibited
Species Type
Aquatic Invasives
DESCRIPTION
Deceptively delicate and fragile in appearance, the Eurasian watermilfoil forms thick mats in shallow areas of a lake, quickly growing and spreading to block sunlight, killing off native aquatic plants that fish and other underwater species rely on for food and shelter.
Note: Research for these pages was generated from citations listed. References for specific statements available upon request.
Leaves: Feather like whorled leaves; long and soft and deeply divided.
Flower: Flower spikes above the water with reddish flowers arranged in 4-flowered whorls along the spike.
Stem: Grows with long branching stems that are submerged and rooted into substrate.
Exact date unknown; between the 1880s and the 1940s.
Means of introduction is unknown, possibly through the aquarium trade or transport of watercraft
North America, the plant threatens the diversity and abundance of native plants as well as the ecological balance of lakes and ponds, which in turn adversely affects recreational opportunities. If left unchecked, invasive watermilfoil will spread through a lake, or even to other lakes by transmission. An expert team of USDA Forest Service divers with invasive species and aquatics expertise is focused on rooting out the plant.
Eurasian watermilfoil can reproduce via fragmentation, meaning a single stem fragment introduced to a waterbody could take root and establish a new population. Although it is present in almost every county in Wisconsin, it has only been verified in less than 10 percent of waterbodies statewide.
Eurasian water-milfoil has adapted to a variety of water conditions and has established colonies in lakes, ponds, reservoirs, and low energy areas of rivers and streams. It can grow in brackish water as well as fresh water, and has an affinity for areas that have been exposed to disturbances, such as nutrient loading, intense plant management and excessive motorboat use. This plant spreads rapidly with multiple means of reproduction. It propagates from seeds, roots and stem fragments, often developing roots before separating from the parent plant. It successfully competes against native plants by its means of reproduction and its ability to grow quickly, stealing sunlight and space from other plants. These plants can also alter the hydrology of waterways, leading to decreased dissolved oxygen content, increased temperatures and pH. They can also have large impacts on recreation, damaging mechanisms of boats, reducing recreational value of nearby locations, and also clogging waterways utilized by facilities
Avoid infested areas or reduce your speed when travelling near Eurasian watermilfoil infestations. Your propeller can break off fragments and spread the pieces to new areas. New plants can grow from small pieces of the plant.
Inspect your boat, trailer, and equipment after each use. Remove all plants, animals, and mud before moving to a new waterbody. Learn more about the process of clean, drain, dry.
Avoid planting Eurasian watermilfoil in your aquarium or water garden. Aquarium hobbyists and water gardeners should only use native or non-invasive plants and are encouraged to ask retailers for plants that are not invasive.
Never release unwanted aquarium plants or pets. Return or donate unwanted plants to a garden centre or pet store, or put them in the garbage. Do not put them in the compost or discard them in natural areas. Discarded plants may produce seeds that can sprout.
