Eurasian water-milfoil

Myriophyllum spicatum L.

U.S. Nativity: Exotic
Habit: Aquatic

Synonym(s): spiked watermilfoil

Myriophyllum spicatum is a submersed aquatic plant that invades lakes, ponds, and other aquatic environments throughout the United States. The plants are rooted and the stems grow up to the water surface, usually reaching 3-10 ft. (0.9-3 m) in length and can be as much as 30 ft. (9.1 m) long.
Leaves are bright green, finely dissected, and whorled. The delicate leaflets give this plant a feathery appearance.
Myriophyllum spicatum has both male and female flowers on the same inflorescence. The female flowers are basal while the male flowers are located distally. The female flowers have a 4-lobed pistil and lack sepals and petals. The male flowers have 4 pink petals and 8 stamens.
The very small globular fruit of Myriophyllum spicatum are indehiscent, and contain 4 seeds.
Ecological Threat
Myriophyllum spicatum requires stagnant to slowly moving water and can tolerate brackish conditions. It forms dense mats of leaves restricting light availability, leading to a decline in the diversity and abundance of native macrophytes. In addition, Myriophyllum spicatum displaces the native species of watermilfoil and reduces habitats for fish spawning and feeding. It is native to Europe, Asia, and northern Africa.

Identification, Biology, Control and Management Resources

Biological Control of Invasive Plants in the Eastern United States - USDA Forest Service
Southeast Exotic Pest Plant Council Invasive Plant Manual - SE-EPPC
Plant Invaders of Mid-Atlantic Natural Areas - National Park Service and U.S. Fish and Wildlife Service
Weeds Gone Wild: Alien Plant Invaders of Natural Areas - Plant Conservation Alliance
Invasive Plant Atlas of New England - University of Connecticut
Global Invasive Species Database - Invasive Species Specialist Group
Images, Video and Information - University of Florida - Center for Aquatic and Invasive Plants
Fact Sheet - Ontarios Invading Species Awareness Program