Fact Sheet from the University of Main Cooperative Extension: Eurasian Milfoil Threats to Native Habitat Eurasian milfoil is a highly aggressive aquatic plant that can form dense mats which congest waterways and crowd out native aquatic plants. Thick growth can impair recreational uses of waterways including boating, swimming, and fishing. Dense growth of Eurasian milfoil can alter and degrade the habitat of native fish and other wildlife. Some stands have been dense enough to obstruct industrial and power-generation water intakes. The visual impact of the flat, yellow-green of matted vegetation on milfoil-dominated lakes often creates the perception that the lake is “infested” or “dead.” Cycling of nutrients from sediments to the water column by Eurasian milfoil may lead to deteriorating water quality and algal blooms on infested lakes. Eurasian milfoil is readily spread by plant fragments, which are abundant in infested waterways. Fragments may be carried downstream by water currents or inadvertently picked up by boaters. Milfoil is readily dispersed by boats, motors, trailers, bilges, live wells or bait buckets, and can stay alive for weeks if kept moist. Description Eurasian water milfoil is an herbaceous perennial plant with a trailing growth habit. Narrow stems grow to the water surface, usually extending three to ten feet, although sometimes much longer. They frequently form dense mats. Stems of Eurasian milfoil are usually branched, and become leafless toward the base. New plants may emerge from each node (joint) on a stem, and root upon contact with mud. Leaves are finely divided and occur in whorls of three or four. Eurasian milfoil produces small yellow flowers on a spike that projects two to four inches above the water surface. Most regeneration of Eurasian water milfoil is from rhizomes, fragmented stems and axillary buds that develop throughout the year. Although seeds are usually viable, they are not an important means of reproduction. Habitat Eurasian milfoil grows best in fertile, fine-textured, inorganic sediments. In less productive lakes it is restricted to areas of nutrient-rich sediments. It is an opportunistic species that prefers highly disturbed lake beds, lakes receiving nitrogen and phosphorus-laden runoff, and heavily used lakes. High water temperatures promote multiple periods of flowering and fragmentation. Habitat for Eurasian milfoil includes lakes, ponds, slow-moving streams, reservoirs, and estuaries. Many of New York’s ponds, lakes, and rivers are vulnerable to infestation by this species.  istribution Eurasian milfoil is native to Europe, Asia and northern Africa. It was introduced to the U.S. in the 1940s. The source of the original introduction is unclear. Now Eurasian milfoil occurs in nearly every state in the U.S. and several Canadian provinces. Spread is mostly attributed to boating activity, although their have been some deliberate introductions. A number of populations found in Oklahoma were introduced by earthworm farmers who packed their product in Eurasian milfoil. As of 2002 there are no documented occurrences of this plant in Maine. Prevention and Control The best way to control this species, or any aquatic invader, is to prevent it from being introduced in the first place. Anyone engaged in activities in Maine’s waters should be aware of the potential for spreading invasive plants and take steps to prevent their introduction; your actions can make a difference. Simple things to do include inspecting boats, motors, and trailers at the boat ramp before launching and again after hauling them out. Prevent plant material from getting into bait buckets and live wells, and from getting tangled up in anchor ropes or fishing gear. Plants cleaned from boats and gear should be disposed of in a trash receptacle or away from water on dry land. Once established, invasive aquatic plants are extremely difficult to eradicate. Control experiments have been attempted with water level manipulations, mechanical control and herbicides. In most cases these plants have survived attempts at control. Biological controls for invasive aquatics are still being researched and may help limit growth of some species in the future. Note that the use of herbicide in Maine waters is strictly regulated. Only licensed professionals with a permit from the Department of Environmental Protection may carry out herbicide treatments in Maine’s waters.