MYRIOPHYLLUM SPICATUM L.
Eurasian water-milfoil; spike water-milfoil
pronounced: mirio-file-um / spi-ka-tum
from: myrios (G.): numberless
phyllon (G.): leaf
spica (L.): spike
“a plant with many leaf divisions, and a spike of flowers”
Eurasian water-milfoil is submersed. It tolerates a wide range of water conditions, and often forms large infestations.
Eurasian water-milfoil stems are reddish-brown to whitish-pink. They are branched and commonly grow to lengths of six to nine feet. The leaves are deeply divided, soft and feather-like. Leaves are about two inches long. The leaves are arranged in whorls of three to six leaves about the stem. The flowers of Eurasian water-milfoil are reddish and very small. They are held above the water on an emersed flower spike that is several inches long.
- Eurasian water-milfoil is a submersed, rooted, perennial
- its stems can “top out” in 20 feet of water, but the plant is most often found in water 0.5 to 3.5 m deep (Aiken et al. 1979)
- often forms large infestations; often is the most abundant submersed species in a locale
- spreads and reproduces mainly by regrowth of plant fragments; spreads locally by stolons
- will halt boat traffic on rivers; will fill a lake surface from shore to shore
- an aquatic weed worldwide
- seems to prefer lakes, ponds and slow-moving rivers and streams but can also grow in fast-moving water (Newroth 1985)
- tolerates a wide range of water conditions, including spring water and even brackish water of tidal creeks and bays with salinity of up to 10 parts per thousand (Beaven 1960)
- temperature tolerance: Eurasian water-milfoil is winter-hardy, able to overwinter in frozen lakes and ponds in northern states and Canada; but is also able to grow in shallow, over-heated bays such as Chassahowitzka Bay in Florida
Myriophyllum spicatum L.
Original description: Linnaeus 1753
- dicot, perennial
- there are a number of water-milfoils, native and non-native, that are confusable; this water-milfoil has decidedly feathery-looking leaves
- plants submersed rooted, attached to the substrate
- stems slender, smooth, 6 to 20 ft. long; stems reddish-brown to whitish-pink; branching several times near the water surface
- leaves are olive-green, less than 2 in. long, soft, deeply divided, feather-like; each leaf with a central axis (midrib) and 14 to 24 or so very slender (filiform) segments on each side of the axis
- leaf whorls are arranged along the stems in whorls of 3 to 6 (usually 4) leaves; whorl nodes are about 3/8 in. apart
- flowers on an emersed spike, held erect above the water, the spike to 8 inches long; flowers reddish; arranged in 4-flowered whorls along spike; petals 4; petals 1/8 in. long; sepals 4; stamens 8; flowering in Canada from late July to early August
- fruit 4-lobed; splitting into 4 nutlets
- roots fibrous; often developing on plant fragments
Myriophyllum spicatum might be confused with a number of other submersed plants, including other water-milfoils and other submersed plants.
- native northern water-milfoil (Myriophyllum sibiricum = M. exalbescens):
- — has fewer than 12 leaf segments on each side of the leaf axis, whereas Eurasian water-milfoil leaves have 14 or more leaf segments on each side of the leaf axis; and has somewhat stouter stems than does Eurasian water-milfoil
native coontail (Ceratophyllum demersum):
- — leaves are toothed and the plant feels rough when pulled through the hand, whereas Eurasian water-milfoil leaves are not toothed and the plant does not feel rough
- there are about 40 species of Myriophyllum in the world
- Some experts believe that Myriophyllum spicatum, Eurasian water-milfoil, originated in Eurasia; others believe northern Africa
- occurs in Europe, Asia, India, Japan, Canada and the U.S.
Distribution in the U.S.
Eurasian water-milfoil is present in most U.S. states and in British Columbia, Ontario and Quebec. The map on the left is based on the older data of Kartesz.
The best way to track the spread of invasive aquatic plants may be to identify the drainage basins (watersheds) they have been discovered in. Drainage maps give useful information to eco-managers because drainage maps show precisely where the plants are, making it easier for managers to infer where the plants might go next, and thus where to take preventive measures.
How it got here
- Myriophyllum spicatum, Eurasian water-milfoil was probably intentionally introduced, possibly by federal authorities, into the U.S. and was first found in 1942 in Washington, D.C. (Couch & Nelson 1985); or the plant was introduced in the late 1800s, possibly in ship ballast, in the Chesapeake Bay area (Aiken et al. 1979)
- may have been spread as packing material for worms sold to fishermen in Oklahoma (Couch & Nelson 1985)
- was first observed in Ontario in the 1960s; was first observed in British Columbia in 1970 in Okanagan Lake
- first found in Minnesota in Lake Minnetonka, in 1987; by 1990 it was in 37 waterbodies; by 1991, 51; and in 1999 was found in 100 waterbodies (R.M. Newman, pers. com.)
- Eurasian water-milfoil is not on the U.S. Federal Noxious Weed List; it continues to be sold through aquarium supply dealers and over the Internet.
Potential to spread elsewhere in U.S.
- Eurasian water-milfoil is being spread by transport of fragments from one water body to another, both by boats and other vehicles and by water currents (Aiken et al. 1979)
- Minnesota authorities found aquatic plants on 23% of all boats and trailers inspected (Bratager 1996)
- it is also cold hardy and tolerant of a variety of water quality conditions
- Myriophyllum spicatum grows quickly to form dense infestations which shade out and replace native plants (Smith & Barko 1990; Madsen 1994; Madsen et al. 1991)
- Eurasian water-milfoil infestations negatively affect birds and fish (Aiken et al. 1979; Madsen et al. 1995)
- decaying mats of Eurasian water-milfoil reduce oxygen levels in the water (Honnell 1992)
Due to decades of university, state and federal research and experience with Myriophyllum spicatum in the U.S. and Canada, several methods have been developed to help in its management.
the use of mechanical harvestors and chopping machines should be carefully considered because resulting plant fragments may easily regrow or be carried downstream to create new infestations; harvesting machines are effective at reducing a large biomass in a short time, however harvesting may have to be done several times per year
In Okanagan Lake, British Columbia, authorities have apparently successfully experimented with management by simultaneously rototilling plants and roots and underwater vacuuming (Newroth 1988)
Water level manipulation (drawdown) has been used effectively to control Eurasian water-milfoil in Tennessee reservoirs (Bates et al. 1985)
years of research to find insect biocontrols has resulted in the successful introduction of insects which are believed to be helping keep Eurasian water-milfoil under control; biocontrol fish also have been successfully used (Bonar et al. 1993.)
registered aquatic herbicides such as endothall, 2,4-D and fluridone do provide temporary control of Eurasian water-milfoil, but efforts to eradicate the plant “are rarely, if ever, likely to succeed” (Smith & Barko 1990)
From the University of Florida Aquatic Weed Management Guide, Vandiver 1999:
- According to this Guide, a number of aquatic herbicides may be used to manage “watermilfoil”, including formulations of endothall, diquat, copper, 2,4-D, and fluridone. A concentration of 5 ppm 2,4-D for 1 h will kill all plants (Steward & Nelson 1972). As always, comply with federal law by following the herbicide label instructions, permissible sites and application rates.
What can you do?
Transporting Eurasian water-milfoil fragments on boats, trailers, and in livewells is the main introduction route to new lakes and rivers. So, clean your boat before you leave the ramp!
But, there’s plenty more you can do to help.
Laws and lists
- is “state-listed” in Florida, Minnesota, North Carolina, South Carolina and Washington
- is on the Florida Prohibited Plants list, Florida Department of Environmental Protection
- is on lists of government agencies and/or pest plant councils in 21 states
- is on the Florida Exotic Pest Plant Council list: Category II – “species that have shown a potential to disrupt native plant communities in Florida”
Want to know more?
The information contained on this wep page was extracted from published scientific literature and agency reports. It is important to know that plant research, like most areas of scientific research, is still relatively young and incomplete–much may have been published about the physiology of one plant but not about its management; much may have been published about how to culture and grow another plant but not about its natural ecology. Thousands of research articles may have been published about one invasive plant, but perhaps only a dozen about another.
If you want to read the research yourself, perhaps to clarify or expand an area of information contained here, or to help determine your own line of research, you are welcome to query the world’s largest collection of international scientific literature about aquatic, wetland and invasive plants, the APIRS bibliographic database, which contains more than 54,000 citations and their content keywords. Or you might want to ask us to do it for you and mail or e-mail the search results to you.
This is the literature about Myriophyllum spicatum that was used to develop this web page. More research items about this plant may be found at APIRS:
- Aiken SG, Newroth PR, Wile I. 1979. The biology of Canadian weeds. 34. Myriophyllum spicatum L. Canadian J. Plant Sci. 59:201-215
- Barko JW. 1983. The growth of Myriophyllum spicatum in relation to selected characteristics of sediment and solution. Aquatic Botany 15:91-103
- Bates AL, Smith CS. 1994. Submersed plant invasions and declines in the southeastern United States. Lake and Reservoir Management 10(1):53-55
- Bertholdt W. 1958. Your aquarium needs Myriophyllum — plant of delicate beauty. Aquarium Journal 29:106-107
- Bonar SA, Thomas GL, Thiesfield SL, Pauley GB, Stables TB. 1993. Effect of triploid grass carp on the aquatic macrophyte community of Devil’s Lake, Oregon. North American Journal Fisheries Management 13(4):757-765
- Bratager M, Crowell W, Enger S, Montz G, Perleberg D, Rendall WJ, Skinner L, Welling CH, Wright D. 1996. Harmful Exotic Species of Aquatic Plants and WIld Animals in Minnesota. Annual Report. Minnesota Department of Natural Resources, St. Paul. 99 pp.
- Budd J, Lillie RA, Rasmussen P. 1995. Morphological characteristics of the aquatic macrophyte, Myriophyllum spicatum L. in Fish LAke, Wisconsin. Journal of Freshwater Ecology 10:19-31
- Couch R, Nelson E. 1985. Myriophyllum spicatum in North America. In: Anderson LWJ, ed., First International Symposium on Watermilfoil and Related Haloragaceae Species, 23-24 July 1985, Vancouver, BC. Aquatic Plant Management Society, Vicksburg, MS.
- Creed RP. 2000. The weevil-watermilfoil interaction at different spatial scales: what we know and what we need to know. J. Aquat. Plant Manage. 38:78-81
- Creed RP, Sheldon SP. 1995. Weevils and watermilfooil: did a North American herbivore cause the decline of an exotic plant? Ecological Applications 5:1113-1121
- Engel S. 1995. Eurasian watermilfoil as a fishery management tool. Fisheries 20(3):20-27
- Fernald ML. 1919. Two new Myriophyllums and a species new to the United States. Rhodora 21:120-124
- Goldsby TL, Bates AL, Stanley RA. 1978. Effect of water level fluctuation and herbicide on Eurasian watermilfoil in MElton Hill Reservoir. Journal of Aquatic Plant Management 16:34-38
- Holm LG, Plucknett DL, Pancho JV, Herberger JP. 1977. The world’s worst weeds: distribution and biology. Honolulu: University Press of Hawaii. 609 pp.
- Honnell D, Madsen JD, Smart RM. 1992. Effects of aquatic plants on water quality in pond ecosystems. In: Proceedings, 26 Annual Meeting, Aquatic Plant Control Research Program, Report A-92-2. US Army Corps of Engineers Waterways Experiment Station, Vicksburg, MS.
- Johnson RL, Van Dusen PJ, Toner JA, Hairston NG. 2000. Eurasian watermilfoil biomass associated with insect herbivores in New York. J. Aquat. Plant Manage. 38:82-88
- Keast A. 1984. The introduced aquatic macrophyte, Myriophyllum spicatum, as habitat for fish and their macroinvertebrate prey. Can. J. Zool. 62:1289-1303
- Lillie RA. 2000. Temporal and spatial changes in milfoil distribution and biomass associated with weevils in Fish Lake, WI. J. Aquat. Plant Manage. 38:98-104
- McCann JA et al. 1996. Nonindigenous aquatic and selected terrestrial species of Florida-Status, pathway, and time of introduction, present distribution, and significant ecological and economic effects. Southeastern Biological Science Center, Gainesville, 256 pp.
- Madsen JD, Smart RM, Dick GO, Honnell DR. 1995. The influence of an exotic submersed aquatic plant, Myriophyllum spicatum, on water quality, vegetation and fish populations of Kirk Pond, Oregon. In: Proceedings, 29 Annual Meeting, Aquatic Plant Control Research Program, US Army Corps of Engineers Waterways Experiment Station, Vicksburg, MS.
- Nelson LS. 1996. Growth regulation of Eurasian watermilfoil with flurprimidol. Journal of Plant Growth Regulation 15:33-38
- Newman RM, Biesboer DD. 2000. A decline of Eurasian watermilfoil in MInnesota associated with the milfoil weevil, Euhrychiopsis lecontei 2000. J. Aquat. Plant Manage. 38:105-111.
- Nichols SA, Buchan LA. 1997. Use of native macrophytes as indicators of suitable Eurasian watermilfoil habitat in Wisconsin lakes. Journal of Aquatic Plant Management 35:21-24
- Sheldon SP. 1994. Invasions and declines of submersed macrophytes in New England, with particular reference to Vermont lakes and herbivorous invertebrates in New England. Lake and Reservoir Management 10(1):13-17
- Smith CG, Barko JW. 1990. Ecology of Eurasian watermilfoil. Journal of Aquatic Plant Management 28:55-64
- Smith CG, Barko, JW. 1996. Evaluation of a Myriophyllum spicatum decline in reservoirs of the Tennessee and Cumberland rivers. Tech. Report A-96-6, US Army Corps of Engineers Waterways Experiment Station, Vicksburg, MS
- Solarz SL, Newman RM. 1996. Oviposition specificity and behavior of the watermilfoil specialist Euhrychiopsis lecontei. Oecologia 106:337-344
- Steward KK, Nelson LL. 1972. Evaluations of controlled release PVC and Attaclay formulations of 2,4-D on Eurasian watermilfoil. Hyacinth Control J. 10:35-37
- Stuckey RL, Moore DL. 1995. Return and increase in abundance of aquatic flowering plants in Put-in-Bay Harbor, Lake Erie, Ohio. Ohio J. Sci. 95(3):261-266
- Vandiver VV. 1999. Florida aquatic weed management guide. Univ. of FL, IFAS, Cooperative Extension Service, Publ. SP-55, 130 pp.
- Verma U, Charudattan R. 1993. Host range of Mycoleptodiscus terrestris, a microbial herbicide candidate for Eurasian watermilfoil, Myriophyllum spicatum. Biological Control 3:271-280
Other web sites that treat Eurasian water-milfoil
USGS Nonindigenous Aquatic Species Fact Sheets
Biocontrol of Eurasian Watermilfoil — University of Minnesota
PCA Alien Plant Working Group Fact Sheet: Eurasian water-milfoil
Development of a biological control program for Eurasian watermilfoil (Myriophyllum spicatum) by M.J.W. Cock, et al. 2008.
View the herbarium specimen image from the University of Florida Herbarium Digital Imaging Projects.
This web page was authored in June, 2001, by Victor Ramey (Center for Aquatic and Invasive Plants, University of Florida), with significant contribution from Barbara Peichel (Sea Grant, University of Minnesota). The information contained herein is based on the literature found in the APIRS database.
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1. From Identification and Biology of Nonnative Plants in Florida’s Natural Areas – Second Edition, by K.A. Langeland, H.M. Cherry, et al. University of Florida-IFAS Pub SP 257. 2008.
2. From Strangers in Paradise, Impact and Management of Nonindigenous Species in Florida, Chapter 2: Florida’s Invasion by Nonindigenous Plants: History, Screening, and Regulation, by D.R. Gordon and K.P. Thomas, pp. 21-37. Island Press, Washington, DC, 1997.