Eurasian watermilfoil is a feathery submerged aquatic plant that was once commonly sold as an aquarium plant. It quickly forms thick, damaging mats that are causing harm in shallow areas of rivers and lakes throughout North America. Species Description Eurasian watermilfoil has small (<2 cm long) feathery leaves that are arranged in whorls of 3-6 (four leaves per whorl is common) around slender stems. The plant grows underwater from roots attached firmly in the sediment. Tiny pink flowers grow on shoots that rise above the water’s surface. In Pennsylvania, these plants usually die back to the roots during the winter. Eurasian watermilfoil may be confused with bladderworts, hornworts, mermaid weeds, and other leafy milfoils. Native & Introduced Ranges Eurasian watermilfoil is native to Europe, Asia, and northern Africa. It was first discovered in the eastern United States in the 1940s, but may have arrived as early as the late 1800s. Since its introduction, it has spread across inland lakes and streams, clinging to boats and waterfowl. The history of its spread in the United States is not well documented because it bears such a close resemblance to native species of watermilfoil; however, it is now known to be established in nearly every U.S. state, and at least three Canadian provinces. In Pennsylvania, Eurasian watermilfoil is common in lakes, ponds, and rivers in all regions of the Commonwealth. Biology & Spread Eurasian watermilfoil does not rely on seeds for reproduction because they germinate poorly under natural conditions. Instead, it reproduces by fragmentation, which is when plant fragments break off and float via water currents, allowing it to disperse long distances. It can also cross land to new waters when these fragments, which can stay alive for weeks if kept moist, hitchhike on boats, boat trailers, motors, and fishing equipment
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