florida Early Detection Network


Eurasian watermilfoil, spiked watermilfoil


Myriophyllum spicatum L.


Watermilfoil family


Myriophyllum spicatum



Incursion II



Synonyms: None


Botanical Glossary

Myriophyllum 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.


Myriophyllum sibiricum Komarov. (Myriophyllum exalbescens Fern.) (Northern watermilfoil), M. verticillatum L. (Whorled watermilfoil)


The 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.


Myriophyllum 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.


The 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.


Aquatic, Lake or Pond, River or Stream ,Salt Marsh. Myriophyllum 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.


Myriophyllum 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.


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 - Includes management information.


Documentation required: Herbarium specimen or mounted snippet of the branch. Best time for documentation: Summer, fall.


Integrated Taxonomic Information System - Has general taxonomic information about the species.

The PLANTS Database - General information and map

Center for Aquatic and Invasive Plants - General information and photographs

Washington State Department of Ecology - General information including control

US Geological Survey - Nonindigenous Aquatic species - General information, maps and detailed distribution

Vermont Department of Environmental Conservation - Water Quality Division -Drawings and general information

University of Minnesota Division of Fisheries and Wildlife - General information including control

Minnesota Sea Grant - Photographs, general information, advice to boaters

Ohio Division of Natural Areas and Preserves - General information including control

Wisconsin Department of Natural Resources - General information and control


Bailey, L. H. 1949. Manual of Cultivated Plants. Macmillan, New York.

Bossard, C.C., Randall J.M., andHoshovsky, M.C. (2000) Invasive plants of California's wildlands. University of California Press, Berkeley, California.

Coffey, B.T. and McNabb, C.D. (1974) Eurasian water-milfoil in Michigan. The Michigan Botanist 13,159-165.

Crow G.E. and C.B. Hellquist. 2000. Aquatic and Wetland Plants of Northeastern North America. Vol 1. University of Wisconsin Press, Madison.

Fernald, M.L. 1950. Gray's Manual of Botany 8th edition. American Book Company, New York.

Gleason H.A. and A.C. Cronquist. 1991. Manual of Vascular Plants of the Northeastern United States and Adjacent Canada. 2nd ed. New York Botanical Garden, Bronx, New York.

Grace, J.B. and Wetzel, R.G. (1978) The production biology of Eurasian watermilfoil (Myriophyllum spicatum L.): a review. Journal of Aquatic Plant Management 16,1-11.

Hoffman, R. and Kearns, K. (1981) Wisconsin Manual of Control Recommendations for ecologically invasive plants. Bureau of Endangered Resources, Wisconsin Department of Natural Resources, Madison, Wisconsin.

Holm,L.G., Doll, J., Holm E., Pancho, J., Herberger, J.(1997). World Weeds. John Wiley and Sons, New York.

Holmgren N.H. 1998. Illustrated Companion to Gleason and Cronquist's Manual. New York Botanical Garden, Bronx, New York.

Kimbel, J.C. and Carpenter, S.R. (1981) Effects of mechanical harvesting on Myriophyllum spicatum L. regrowth and carbohydrate allocation to roots and shoots. Aquatic Botany 11, 121-127

Les, D.H. and L.J. Mehrhoff. 1999. Introduction of nonindigenous aquatic vascular plants in southern New England: a historical perspective. Biological Invasions 1:281-300.

Madsen, J.D., Sutherlan, J.W., Bloomfield, J.A., Eichler, L.W., and Boylen, C.W. (1991) The decline of native vegetation under dense Eurasian watermilfoil canopies. Journal of Aquatic Plant Management 29, 94-99.

Magee D.W and H.E. Ahles. 1999. Flora of the Northeast. University of Massachusetts Press, Amherst.

Moody, M. and D. Les. 2002. Evidence of hybridity in invasive watermilfoil populations. PNAS 99:14867-14871.

Patten Jr., B.C. 1956. Notes on the biology of Myriophyllum spciatum L. in a New Jersey lake. Bulletin of the Torrey Botanical Club 83(1):5-18.

USDA, NRCS. 2001. The PLANTS Database, Version 3.1. (//plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.