Species & plants
Eurasian watermilfoil
Also known as: Myriophyllum spicatum, milfoil
Eurasian watermilfoil (Myriophyllum spicatum) is the dominant submerged invasive across the upper Midwest, Northeast, and Pacific Northwest. Identified by whorls of 4 feather-like leaves with 12+ pairs of thread-thin leaflets per leaf — more than the native northern milfoil. Reddish-brown stems snap easily; a single boat-prop pass can scatter 50+ viable fragments, each rooting in 5–10 days. Hybridizes with native northern milfoil to produce hybrid milfoil, which is increasingly common in Wisconsin and Minnesota and harder to control with most herbicides.
Related terms
- FluridoneA systemic aquatic herbicide used for hydrilla, milfoil, and other submerged invasives at very low concentrations.
- EndothallA contact aquatic herbicide for hydrilla, pondweeds, and milfoil; faster-acting than fluridone.
- Triploid grass carpSterile grass carp stocked at 5–15 fish per acre to graze hydrilla and other tender submerged vegetation.
Related articles
- Aquatic invasive weeds in the United States: identification guideNine invasive aquatic plants cause the majority of waterway damage across the United States. Here's how to identify each one before treatment.
- How fast do aquatic weeds grow? Spread rates of major invasivesWater hyacinth doubles in under two weeks. Hydrilla puts on four inches a day. Knowing the actual numbers changes when — and whether — to act.