Eurasian Watermilfoil
Myriophyllum spicatum

Origin: Eurasia and Africa

Background
Introduced accidentally from Eurasia in the 1940s, Eurasian milfoil possibly escaped from an aquarium or was brought in on a commercial or private boat.

Description
A n herbaceous aquatic plant in the water-milfoil family (Haloragaceae); stems grow to the water surface, usually extending 3 to 10 feet but as much as 33 feet in length and frequently forming dense mats; stems are long, slender, branching, hairless and become leafless toward the base; new plants may emerge from each node (joint) on a stem and root upon contact with mud. Bright green leaves are finely divided and occur in whorls of three or four along the stem, with 12 to 16 pairs of fine, thin leaflets about 1/2 inch long. These leaflets give milfoil a feathery appearance that is a distinguishing feature of the plant. Eurasian watermilfoil produces small, yellow, four-parted flowers on a spike that projects 2 to 4 inches above the water surface. Flower spikes often remain above water until pollination is complete. The fruit is a hard, segmented capsule containing four seeds. Spreads by rhizomes, fragmented stems and axillary buds that develop throughout the year. Although seeds are usually viable, they are not an important means of dispersal.