Originated in Europe, Asia, and northern Africa, accidentally introduced to America in the 1940s.
A submersed aquatic perennial with branching stem up to 20 feet long. This plant forms dense mats that lie on the surface of the water. Stems vary in color from green to usually red near the apex of the stem. Like the native milfoils, the Eurasian variety has slender stems whorled by submersed feathery leaves and tiny yellow four petaled flowers produced above the water surface.
The flowers are located in the axils of the floral bracts. The leaves are threadlike, typically uniform in diameter, and have a submersed terminal spike. The stem thickens below the water and doubles its width further down, often curving to lie parallel with the water surface. The fruits are 4-jointed nut-like bodies. Without flowers or fruits, Eurasian water milfoil is nearly impossible to distinguish from Northern water milfoil. Eurasian water milfoil grows best in fertile, fine-textured, inorganic sediments. It also does well in disturbed or oxygen-poor water and can tolerate high pollution levels.
Fragments of this plant can re sprout causing even further spread. Plants can become fragmented by boats and water birds. Milfoil is readily dispersed by boats, motors, trailers, live wells, or baits buckets, and can stay alive for weeks if kept moist.
The thick mats prevent light from penetrating the dense cover and end up shading out native aquatic plant species. Decomposing mats alter oxygen levels and water temperature. This in turn makes water unsuitable for fish and other wildlife. Dense mats also can interfere with recreation and water traffic.
Milfoil is best controlled in waterways by means of large harvesting equipment to catch and dispose of the plant. For very small areas, rakes can be useful in removing the plant. Water level adjustment and chemical treatment are also possible methods of control, but require further study of the waterway to assess impact. Please be sure to inspect your canoe, kayak, or boat before leaving a site to prevent spreading this invasive plant to other water bodies. Washing or rinsing the underside at the site is recommended. Any removal within 100 feet of wetland resource areas, including certified vernal pools, or within 200 feet of a perennial stream may require approval from the Concord Natural Resources Commission. Please contact the Division of Natural Resources before you begin.
The following native plants can serve as a good replacement to milfoil: