Identification: Hydrocharis morsus-ranae is a free-floating aquatic plant with leathery, heart-shaped leaves and small white flowers with three petals. The root system is well developed, but does not normally anchor the plant to the substrate. The species spreads by sending out runners, and can form dense, tangled mats (Environment Canada 2003).
The growth form is stoloniferous, the stolons having seasonally dimorphic terminal buds with one root. The leaves are petiolate and floating or, in dense vegetation, emergent. The leaf blade is ovate to orbicular in shape, typically measuring 1.2-6 x 1.3-6.3 cm, with a chordate to reniform base, and entire margin. Veination is palmate with cross-veins. The primary veins form a 75--90° angle with the midvein and are broadly curving. Aerenchyma are confined to the midvein region (not margin to margin as in Limnobium). Individual aerenchyma space, located approximately 1 mm from either side of midvein, typically measures 0.1-0.5 mm across its longest axis (eFloras 2008; Gleason and Cronquist 1991).
The species is dieocious (male and female flowers found on separate plants). Both sexes of flowers have an outer whorl of three greenish-red sepals, and a whorl of three membranous white petals. Staminate (male) flowers occur in cymose inflorescences of 2 to 5 flowers on pedicels up to 4 cm long. The inflorescence is enclosed by a spathe of one or two scale leaves which subtend the first two flowers. The stamens number 9 to 12 and are arranged in 3 trimerous whorls, with an innermost whorl of staminodes. The first and third whorls of stamens are partially united along their filaments, and the second whorl of stamens is fused to the staminodes. The anthers are basifixed and consist of four micro-sporangia, with pollen grains dehiscing through lateral slits. In the center, there is a large pistil-like structure (Scribailo and Polsluzny 1985).
Pistillate (female) flowers are solitary and enveloped in a tubular hypanthium, with pedicels up to 9 cm long. The ovary is inferior, with six dorsiventral styles. Each style is bifurcated at the end into two flat, papillose stigmas. There is a whorl of nectaries that occur as appendages on the three antipetalous styles, and a whorl of filament-like staminodes. The fruit is a berry that dehisces longitudinally, releasing seeds 1 to 1.3 mm in length (Scribailo and Polsluzny 1985).
References: (click for full references)
Aquatic Ecosystem Restoration Foundation (AERF). 2013. Aquatic Herbicides/Agents. Available http://www.aquatics.org/herbicides.html
. Accessed 16 April 2013.
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.
Catling, P.M. and W.G. Dore. 1982. Status and identification of Hydrocharis morus-ranae and Limnobium spongia (Hydrocharitaceae) in northeastern North America. Rhodora 84(840):523-545.
Catling, P. M., G. Mitrow, E. Haber, U. Posluszny, and W. A. Charlton. 2003. The biology of Canadian weeds. 124. Hydrocharis morsus-ranae L. Canadian Journal of Plant Science 83:1001—1016.
Catling, P.M., K.W. Spicer, and L.P. Lefkovitch. 1988. Effects of the introduced floating vascular aquatic, Hydrocharis morsus-ranae (Hydrocharitaceae), on some North American aquatic macrophytes. Naturaliste Canadien 115:131-137.
Cutter, E. G. 1964. Observations of leaf and bud formation in Hydrocharis morsus-ranae. American Journal of Botany 51(3): 318—324.
Daniels, J. 2000. European Frogbit: What is it? Should we be worried? Michigan Sea Grant College Program, Upwellings 22(4).
Environment Canada. 2003. Factsheet for European Frog-bit (Hydrocharis morsus-ranae).
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. efloras.org
Gleason, H. A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, NY.
Grant, M. S. 2013. Frogbit. Available http://www.miseagrant.umich.edu/explore/native-and-invasive-species/species/plants/frogbit/. Accessed 16 April 2013.
Great Lakes Panel of Aquatic Nusiance Species (GLPANS). 2008. Prohibitied Species in the Great Lakes Region. 14 pp.
Haynes, R. R. 1988. Reproductive biology of selected aquatic plants. Annals of Missouri Botanical Garden 75(3): 805—810.
Illinois Department of Natural Resources (IL DNR). 2009. Aquatic Invasive Species: European Frog-bit. Available http://www.in.gov/dnr/files/EUROPEAN_FROG-BIT.pdf. Accessed 16 April 2013.
Invasive Plants of Canada Database. 1995. USA records of Hydrocharis morsus-ranae in the Collections of Agriculture and AgriFoods Canada, Central Experimental Farm, Ottawa, Ontario (DAO). Compiled by Erich Haber, Ph.D., National Botanical Services, Ottawa.
Lui, K., M. Butler, M. Allen, E. Snyder, J. da Silva, B. Brownson, and A. Ecclestone. 2010. Field Guide to Aqautic Invasive Species: Identification, collection and reporting of aquatic invasive in Ontario waters. Minstry of Natural Resources, Ontario, Canada. 201 pp.
Mikulyuk, A. and M. Nault. 2011. Hydrocharis morsus-ranae. Available http://www.cabi.org/isc/default.aspx?site=144&page=481&LoadModule=DataSheet&dsID=28140&CompID=5. Accessed 16 April 2013.
Minnesota Department of Natural Resources (MN DNR). 2013. Minnesota invasive species laws. Available http://www.dnr.state.mn.us/invasives/laws.html. Accessed 16 April 2013.
Mudrzynski, B., D.A. Wilcox, and A. Heminway. 2011. Habitats Invaded by European Frogbit (Hydrocharis morsus-ranae) in Lake Ontario Coastal Wetlands. The College at Brockport, State University of New York. 28 pp.
New York Invasive Species Council. 2010. Final report: a regulatory system for non-native species. Department of Environmental Conservation, Albany, NY. 131 pp.
O'Neill Jr., C. R. 2007. European Frog-Bit (Hydrocharis morsus-ranae)- Floating Invader of Great Lakes Basin Waters. New York Sea Grant. 4 pp.
Ontario Invasive Plants Council (OIPC). 2012. #21 European Frogbit. Available www.ontarioinvasiveplants.ca. Accessed 16 April 2013.
Reznicek A.A., E. G. Voss, & B. S. Walters. 2011. MICHIGAN FLORA ONLINE. University of Michigan.
Available http://www.michiganflora.net/species.aspx?id=1449. Accessed 16 April 2013.
Sager, L. and C. Clerc. 2006. Factors influencing the distribution of Hydrocharis morsus-ranae L. and Rumex hydrolapathum Huds. in a mowed low-lying marshland, Reserve de Cheyres, lac de Neuchatel, Switzerland. Hydrobiologia 570: 223-229.
Sarneel, J. M. 2012. The dispersal capacity of vegetative propagules of riparian fen species. Hydrobiologia (online) 7 pp.
Scribailo, R. W. and U. Posluzny. 1985. Floral development of Hydrocharis morsus-ranae (Hydrocharitaceae). American Journal of Botany 72(10): 1578-1589.
Thomas, J. D. and P. W. G. Daldorph. 1991. Evaluation of bioengineering approaches aimed at controlling pulmonate snails: The effects of light attenuation and mechanical removal of macrophytes. Journal of Applied Ecology 28(2): 532—546.
Trebitz, A. S. and D. L. Taylor. 2007. Exotic and invasive aquatic plants in Great Lakes coastal wetlands: distribution and relation to watershed land use and plant richness and cover. Journal of Great Lakes Research 33(4): 705—721.
U. S. Environmental Protection Agency (U.S. EPA). 2008. Predicting future introductions of nonindigenous species to the Great Lakes. Washington DC. 138 pp.
University of Minnesota; Wisconsin Sea Grant Institute. 2003. European Frogbit. Available http://www.seagrant.umn.edu/exotics/frogbit_card.pdf. Accessed 16 April 2013.
University of Minnesota; Wisconsin Sea Grant Institute. 2012. European Frog-Bit (Hydrocharis morsus-ranae). Available http://www.seagrant.wisc.edu/Home/Topics/InvasiveSpecies/Details.aspx?PostID=649
Accessed 16 April 2013.
Villanueva, V. R., L.K. Simolat, and M. Mardon. 1985. Polyamines in turions and young plants of Hydrocharis morsus-ranae and Utricularia intermedia. Phytochemistry 24(1): 171—172
Wisconsin Department of Natural Resrouces (WI DNR). 2012. European frog-bit (Hydrocharis morsus-ranae). Available http://dnr.wi.gov/topic/Invasives/fact/EuropeanFrogbit.html. Accessed 17 April 2013.
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.