Myriophyllum spicatum (Spiked Water-milfoil or Eurasian water milfoil) is a species of Myriophyllum native to Europe, Asia, and north Africa. It is a submerged aquatic plant, and grows in still or slow-moving water.
Eurasian has slender stems up to 3 m long. The leaves are borne in whorls of four, bipinnate, with the numerous leaflets thread-like, 4-13 mm long. The flowers are produced in the leaf axils on a spike 5-15 cm long held vertically above the water surface, each flower inconspicuous, orange-red, 4-6 mm long. Eurasian water milfoil has 12- 21 pairs of leaflets while North American watermilfoil only has 5-9 pairs.
It has been introduced to North America between the 1950s and 1980's where it has become an invasive species in some areas. As of 2003 Eurasian watermilfoil was found in every state of the contiguous US save for Wyoming and Montana, with Rhode Island, New York, New Jersey, Michigan, Minnesota, and Washington state having the largest areas of infestation. It is commonly believed that people who brought the Eurasian Milfoil to North America in the 1950s were the first to introduce this invasive species.
In lakes or other aquatic areas where native aquatic plants are not well established, the Eurasian plant can quickly spread. It has been known to crowd out native plants and create dense mats that interfere with recreational activity. Eurasian watermilfoil can grow from broken off stems which increases the rate in which the plant can spread and grow. In some areas, the Eurasian Watermilfoil is an Aquatic Nuisance Species.