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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: European water-clover

Synonyms and Other Names: European waterclover, European water-clover, Water shamrock, Pepperwort, Four-leaf clover

Taxonomy: available through www.itis.gov

Identification: This herbaceous, perennial fern grows in aquatic environments from creeping, fleshing roots containing rhizomes (Benson et al. 2004, MIPN.org 2008). It has thin green stalk-bearing downy fiddleheads (furled leaflets) which will open to reveal four wedge-shaped leaflets (Benson et al. 2004, Connecticut Aquatic 2006, MIPN.org 2008). These 1.5 — 4 cm leaflets will float along the water’s surface or be slightly emerged (Benson et al. 2004, Campbell et al. 2010).

Marsilea quadrifolia produces thick sporocarps (spore-producing tissues) on 1—12 mm stalks near the petiole; they are oval and hairy in appearance (Benson et al. 2004, Campbell et al. 2010).

 

Size: max. 20 cm

Native Range: Found in Caucasia, western Siberia, Afghanistan, southwest India, China, Japan and North America.

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: Marsilea quadrifolia requires moist soils and can be found in shallow, slow-moving waters environments: rivers, streams, ponds, shorelines, and ditches (Benson et al. 2004, Campbell et al. 2010). This plant prefers sandy and loamy soils. It can grow in semi-shade or no shade. From creeping rhizomes, thin green stalks rise to the water surface, each stalk bearing a single leaf with four wedge-shaped leaflets (Connecticut Aquatic 2006). When the leaves float on or just below the water surface, the leaflets have an elongated shape (Liu 1984). However in very shallow water, the stalks often are able emerge above the water’s surface and produce the characteristic four-leaf clover shape (Liu 1984).

The rhizomal structure of M. quadrifolia enables this species to reproduce vegetativley (Campbell et al. 2010). This plant also produces sporocarps (spore-producing tissues); male and female spores germinate and cross-fertilize to produce new plants (Benson et al. 2004). The sporocarps also be dispersed by waterfowl and/or remain dormant in the soil for decades (Benson et al. 2004, Campbell et al. 2010)

Means of Introduction: 1925, deliberate release, Lake Ontario drainage (U.S. EPA 2008). Ornamental deliberate release. Many of the localities from which it is known at present are artificial bodies of water. This may indicate intentional introduction of the plant as a curiosity.

Status: It has escaped cultivation and is well established in much of the Northeastern U.S. west to Iowa and Missouri for over 100 years.

Impact of Introduction: Marsilea quadrifolia may out-compete native wetland plants by forming dense stands, although direct evidence of competition or habitat alteration is lacking.

Remarks: Marsilea minuta and M. mutica are often mistaken for M. quadrifolia, all three being glabrous, soft and fleshy when fresh. Nevertheless, the two newly documented exotic species appear better suited to the warmer climate of the Southeast, while more than a century after its initial introduction M. quadrifolia has not extended south of Maryland, Kentucky or Missouri (Henry 1983, Johnson 1993, Jacono & Johnson 2006).

Confusion with other species:
Because its leaves are glabrous to essentially glabrous, Marsilea quadrifolia is unlikely to be confused with any other Marsilea in the flora. Likewise, the petioles of the land leaves in this species tend to be procumbent rather than stiffly erect as in the others. The branched sporocarp stalks found in M . quadrifolia are found elsewhere only in M . macropoda; the latter, however, is a hairy plant and has no distal tooth on the very large sporocarp. Marsilea minuta Linnaeus, a widespread species in the paleotropics, has recently been collected from the Florida Panhandle. It resembles M. quadrifolia in having roots both at the nodes and on the internodes and in having relatively glabrous land leaves, but it has sporocarps that are only 1.3--1.7 mm thick, with a distal tooth 0.3--0.6 mm long. Marsilea minuta also has a tendency for the terminal margins of the land leaves to be crenate rather than entire.

Many ferns also contain thiaminase, an enzyme that robs the body of its vitamin B complex. In small quantities this enzyme will do no harm to people eating an adequate diet that is rich in vitamin B, though large quantities can cause severe health problems. The enzyme is destroyed by heat or thorough drying, thus cooking the plant will remove the thiaminase (Plants For A Future, 2014).

References: (click for full references)

Aida, M., K. Itoh, H. Ikeda, N.  Harada, Y. Ishi, and K. Usui. 2004. Susceptibilities of some aqautic ferns to paddy herbicide bensulfuron methyl. Weed Biology and Management 4:127—135.

Benson, A. J., C.C. Jacono, P.L. Fuller, E. R. McKercher., and M. M. Richerson. 2004. Summary Report of Nonindigenous Aquatic Species in U.S. Fish and Wildlife Service Region 5. U.S. Fish and Wildlife Service, Arlington, Va. 145 pp.

Bhadra, S., P.K. Mukherjee, and A. Bandyopadhyay. 2012. Cholinesterase inhibition activity of Marsilea quadrifolia Linn. an edible leafy vegetable form West Bengal, India. Natural Product Research 26(16): 1519—1522.

Campbell, S., P. Higman, B. Slaughter, and E. Schools. 2010. A Field Guide to Invasive Plants of Aquatic and Wetland Habitats for Michigan. Michigan DNRE, Michigan State University Extension, Michigan Natural Features Inventory. 90 pp.

Connecticut Aquatic Nuisance Species Working Group. 2006. Connecticut Aquatic Nuisance Species Management Plan. State of Connecticut Department of Environmental Protection. 117 pp.

Dewanji, A., S. Matai, L. Si, S. Barik, and A. Nag. 1993. Chemical composition of two semi-aquatic  plants for food use. Plants Foods for Human Nutrition 44(1): 11—16

Falck, M. and S. Garske. 2003. Invasive Non-native Plant Management During 2002. Great Lakes Indian Fish & Wildlife Commission (GLIFWC), Odanah, WI. 68 pp.

Flora of North America. 2008. www.eFloras.org

Great Lakes Panel on Aquatic Nuisance Species (GLPANS). 2008. Prohibitied Species in the Great Lakes Region. 14 pp.

Henry, R.D. 1983. Spread of Marsilea quadrifolia in McDonough County, Illinois. Amer. Fern J. 73: 30.

Henry, R.D. and R.M. Myers. 1983. Spread of Marsilea quadrifolia in McDonough County, Illinois. American Fern Journal 73(1): 30

Illinois Department of Natural Resources. 1996. Minnesota's List of Endangered, Threatened, and Special Concern Species. 16 pp.

Illinois Department of Natural Resources. 2013. Illinois Exotic Species: waterclover Marsilea quadrifolia http://www.dnr.state.il.us/education/exoticspecies/waterclover.htm. 8 April 2013.

Jacono, C.C and Johnson, D.M.  2006. Water-clover Ferns, Marsilea, in the Southeastern United States. Castanea 71 (1): 1–14.

Johnson, D. M. 1986. Systematics of the New World species of Marsilea (Marsileaceae). Syst. Bot. Monogr. 11: 1-87.  

Kao, W.-K. and B.-L. Lin. 2010. Phototropic leaf movements and photosynthetic performance in an amphibious fern, Marsilea quadrifolia. Journal of Plant Research 123(5): 645—653.

Liu, L. B.-L. 1984. Abscisic acid induces land form characteristics in Marsilea quadrifolia L. American Journal of Botany 71(5): pp. 638—644.

Luo, X.-Y. and H. Ikeda. 2007. Effects of four rice herbicides on the growth of an aquatic fern, Marsilea quadrifolia L. Weed Biology and Management 7:237—241.

Meyer, B.N., N.R. Ferrigni, J.E. Putnam, J.B. Jacobsen, D.E. Nicholsand and J.L. Mclaughlin, 1982. Brine shrimp; a convenient general bioassay for activeplant constituents. Planta Medica 45: 31-34.

Mickel, J. T. & A. R. Smith. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88:1-1054.  

Midwest Invasive Plant Network (MIPN.org). 2008. Keep a Look Out for New Aquatic Invasive Plants in the Midwest!, National Park Service. 2 pp.

New York Invasive Species Council. 2010. Final report: a regulatory system for non-native species. Department of Environmental Conservation, Albany, NY. 131 pp.

Ripe, F. A., L. Nahar, M. Haque, and M. M. Islam. 2009. Antibacterial, cytotoxic, and antioxidant activity of crude extract of Marsilea quadrifolia. European Journal of Scientific Research 33(1): 123—129

Sahu, S., G. Dutta, N. Mandal, A.R. Goswami, and T. Ghosh. 2012. Anticonvulsant effect of Marsilea quadrifolia Linn. on pentylenetetrazole induced seizure: a behavioral and EEG study in rats. Journal of Enthnopharmacology 141(1): 537—541.

U.S. EPA (Environmental Protection Agency). (2008) Predicting future introductions of nonindigenous species to the Great Lakes. National Center for Environmental Assessment, Washington, DC; EPA/600/R-08/066F. Available from the National Technical Information Service, Springfield, VA, and http://www.epa.gov/ncea.

Other Resources:
Plant For A Future-Species Database (1997-2000). http://www.pfaf.org/index.php

USDA/NRCS PLANTS Database

Author: Cao, L, and L. Berent

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.