Eurasian Milfoil is an invasive plant species that originates in Europe and Asia. An invasive plant has the ability to thrive and spread aggressively outside its native range. This is harmful to the local ecosystem and has the potential to greatly reduce the natural biodiversity of an area by outcompeting native species. This is a submersed plant species with greater stem diameter below the inflorescence, and with reddish stem tips. Leaves are rectangular with more than 12 pairs of leaflets per leaf, and are dissected to give a feathery appearance, arranged in a whorl. Whorls are approximately 2.5 centimeters apart. Eurasian milfoil grows small, pinkish male flowers that occur on reddish spikes, and female flowers that have a 4-lobed pistil, but lack petals and sepals. Fruits are round (2-3 mm) and contain four seeds. This plant species reproduces via seeds and fragmentation. It can be easily confused with variable-leaf watermilfoil (M. heteropyllum), low watermilfoil (M. humile), northern watermilfoil (M. sibiricum), and whorled watermilfoil (M. verticillatum).
Connecticut's Invasive Aquatic and Wetland Plants Identification Guide, Bulletin 1027, Invasive Aquatic Plant Program, The Connecticut Agricultural Experimentation Station
Invasive Plant Species, National Agricultural Library, United States Department of Agriculture