Myriophyllum aquaticum (Vell.) Verdc.
Synonym(s): parrotfeather watermilfoil, water-feather, Brazilian water-milfoil, parrotfeather

Parrotfeather watermilfoil is an herbaceous, rooted, submerged/emergent plant that invades aquatic habitats throughout much of the United States. Stems are stout and blue-green in color. Leaves are abundant, whorled, pinnately compound, and finely dissected. Submersed leaves are 0.6-1.4 in. (1.5-3.5 cm) long and have 20 to 30 divisions per leaf. Emergent leaves are 0.8-2 in. (2-5 cm) long, less divided and greener than the submersed leaves. As only female plants occur in North America, reproduction occurs vegetatively. Inconspicuous flowers are formed in the axils of the emergent leaves in the spring (sometimes fall). Parrotfeather watermilfoil is found in lakes, ponds, and slow moving streams where it can form dense mats of vegetation. These mats can clog waterways, impede boating traffic, disrupt the growth of native vegetation and provide a breeding ground for mosquitoes. Parrotfeather watermilfoil is native to South America and was first introduced into the United States in the Washington DC area around 1890 as an aquarium and aquatic garden plant.

Identification, Biology, Control and Management Resources