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COMMON NAME Eurasian watermilfoil FULL SCIENTIFIC NAMEMyriophyllum spicatum L. FAMILY NAME COMMONWatermilfoil family FAMILY SCIENTIFIC NAMEHaloragaceae IMAGES
NOMENCLATURE/SYNONYMSSynonyms: None DESCRIPTIONMyriophyllum spicatum is a submerged, aquatic perennial that can have green, reddish-brown or whitish pink stems 1.8-6 m (6-20 ft.) long. The leaves are olive green in color, and less than 5 cm (2 in.) long. They are soft and feather-like in texture, and each mature submerged leaf has a central midrib with 12-20 filiform segments on each side. There are 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 globular fruit are indehiscent, 2-3 mm (0.08-0.11 in.) long and contain 4 seeds. Page References Crow & Hellquist 194, Fernald 1073, Gleason & Cronquist 308, Holmgren 290, Magee & Ahles 772. See reference section below for full citations. SIMILAR SPECIES Myriophyllum sibiricum Komarov. (Myriophyllum exalbescens Fern.) (Northern watermilfoil)
REPRODUCTIVE/DISPERSAL MECHANISMSThe main mechanism of dispersal is the breaking off and relocating of vegetative parts. The seeds can germinate, but may remain dormant for long periods of time.
DISTRIBUTIONMyriophyllum spicatum is native to Europe, parts of Asia and North Africa. In Canada it is present in British Columbia, Ontario and Quebec. In the United States, there are varying distributions reported for Myriophyllum spicatum; It has been reported from all states except Hawaii, Wyoming and Maine. In New England it has been reported from Vermont, New Hampshire, Massachusetts, Connecticut and Rhode Island.
HISTORY OF INTRODUCTION IN NEW ENGLANDThe first report of this plant in the U.S. was in 1942 in a small pond in Washington, DC. Since then, it has been reported from most states rather sporadically, indicating multiple introductions. These introductions were either via the dumping of aquaria into local waterbodies, escape from cultivation or by being attached to boats. It has been present in New England since at least 1962. The first record for Connecticut was in 1979 in East Thompson, though it may have been here earlier.
HABITATS IN NEW ENGLAND,Aquatic,Lake or Pond,River or Stream,Salt MarshMyriophyllum spicatum will grow in water from 0.5-4.5 m (1.6-15 ft.) deep, but is often in the lower end of this range. It can grow in both still and running water. This plant can tolerate highly alkaline water and prefers eutrophic conditions. It can even tolerate brackish water.
THREATSMyriophyllum spicatum forms extremely dense mats of vegetation that can crowd out native aquatic plants. It can tolerate high alkalinity and eutrophic conditions. Mosquitoes find good breeding ground among the mats of vegetation. When these dense mats of plants decompose the oxygen levels in the waterbody are reduced. These dense mats can also alter the temperature profile of a pond or lake. Myriophyllum spicatum plants have a negative affect on bird and fish habitat because of the reduction of oxygen, change in temperature, and change in pH that they cause. These plants can tolerate brackish water, making them a threat in coastal situations as well. The roots overwinter, allowing their persistence in northern climates. Since new plants can grow from fragments, the plant is easily dispersed by boats and waterfowl. This plant impedes recreational activities such as swimming, fishing and boating. Myriophyllum spicatum is known to hybridize with the native M. sibiricum, and encroaches on the range of this native species. The hybrid also forms monotypic invasive populations, but has not yet been identified in New England. MANAGEMENT LINKS Wisconsin Department of Natural Resources Washington State Department of Ecology University of Minnesota Division of Fisheries and Wildlife New Hampshire Department of Environmental Services Ohio Division of Natural Areas and Preserves Environment Canada- Canadian Wildlife Service Plant Conservation Alliance fact sheet DOCUMENTATION NEEDS Documentation required: Herbarium specimen or mounted snippet of the branch.
ADDITIONAL INFORMATION Integrated Taxonomic Information System The PLANTS database Center for Aquatic and Invasive Plants, University of Florida Washington State Department of Ecology US Army Corps of Engineers, Waterways Experiment Station US Geological Survey- Nonindigenous Aquatic species Vermont Department of Environmental Conservation- Water Quality Division University of Minnesota Division of Fisheries and Wildlife Virginia Native Plant Society Minnesota Sea Grant New Hampshire Department of Environmental Services Ohio Division of Natural Areas and Preserves Invasivespecies.gov Environment Canada- Canadian Wildlife Service Wisconsin Department of Natural Resources DATA RETRIEVALDataMAPS OF PLANT DISTRIBUTION IN NEW ENGLANDMap
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