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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: flowering rush

Synonyms and Other Names: Grassy rush; Water gladiolus; Butomus junceus Turcz.

Taxonomy: available through www.itis.gov

Identification: Butomus umbellatus is a moderately tall, rush-like perennial. Plants are stemless and rhizomatous. Its leaves are basal originating from a stout rhizome that is stiff and erect when immersed or lax and floating when in deep water. The inflorescence is a many-flowered umbel borne from a naked scape (stalk). The flowers are perfect, regular, 2-3 cm across, and pink. There are 3 sepals, which are petaloid (tepals). There are 3 petals and 9 stamens with elongate anthers. It has 6 pistils that are simple, whorled, and united at the base. Its fruit is an indehiscent, many-seeded follicle (GISD, 2005).

Butomus can be distinguished by the twisting leaves, which are triangular in cross section, and the inflorescence, with its scape (stalk) also triangular in cross section and umbel of up to 25 flowers showing pinkish tepals (both sepals and petals).

Size: up to 1.5 m high

Native Range: Africa, Asia, and Eurasia (USDA NRCS, 2008)

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

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

Ecology: Butomus umbellatus grows in lakes, riparian zones, water courses, wetlands, and marshes. It can tolerate water as deep or deeper than 2 meters, where cattail is normally found, and can extend to the deepest range of native emergent marsh species (except possibly for hard-stem bulrush and wild rice). Once established in a marsh, populations tend to increase and persist indefinitely. Water level fluctuations may promote the spread of B. umbellatus, allowing populations to expand when water levels are low, and the soil surface is exposed and warmed (Hroudová et al. 1996). However, severe or long-lasting decreases in water level could result in the reduction of B. umbellatus populations (e.g., Hudon 2004). It is intolerant of salt or brackish water (55-153 mg/L) and prefers slightly alkaline sites (pH 7.3-7.6) (Les 2020).

Butomus umbellatus is a perennial plant. Growing season is from May to June, with peak biomass by July. It is in flower from June to October, and the seeds ripen from July to October (in North America) (Les 2020). The scented flowers are hermaphroditic and are obligately pollinated by bees, flies, and lepidopterans. Although Canadian populations of B. umbellatus appeared to be incapable of autonomous seed production (without external pollination assistance), plants were self compatible and produced more seed when self-pollinated (Eckert et al. 2000).

Flowering rush can be fertile (both spread by sexual reproduction and seeds or by vegetative means) or sterile (can only reproduce by vegetative means (Lui et al. 2005, Parkinson et al. 2010). Diploid populations of B. umbellatus can reproduce sexually via seed production and clonally via the branching and fragmentation of rhizomes and the production of small bulbils on both the rhizomes and inflorescences (Lui et al. 2005). Most B. umbellatus populations in the Great Lakes are diploid and capable of producing abundant viable seed, although the major method of reproduction appears to be clonal (Lui et al. 2005). Seeds germinate after cold stratification for several months in water followed by an 8/16-hour light/dark phase in the Spring months. Viability remains for about 68% of seeds after five years in cold water (Les 2020). Sterile triploid populations of B. umbellatus also exist in the Great Lakes region. North American triploid populations rarely flower and also have a limited ability to multiply and disperse via clonal reproduction, although they may have a greater ecological tolerance than diploid populations as a result of polyploidy or of greater investment in vegetative growth (Lui et al. 2005). Triploid populations also appear to be spread more commonly through the horticulture trade. Lui et al. (2005) suggested that these different reproductive strategies are indications of two different forms of B. umbellatus in North America with different life histories and invasion histories.

Diploid and triploid populations of B. umbellatus exist throughout its global range, although reproductive traits and strategies may differ by region (e.g., North American vs. European populations) (Hroudová and Zákravský 1993, Lui et al. 2005). Relative to native European populations, Brown and Eckert (2005) found that nonindigenous North American diploid populations invested much more biomass in reproduction and were more likely to produce both inflorescences and clonal bulbils. Post-establishment survival was also over twice as high for North American populations as it was for European populations (Brown and Eckert 2005).

Flowering rush has a very wide range of hardiness (zones 3-10) which makes it capable of being widely invasive in the United States (IPANE 2001).

Means of Introduction: Butomus umbellatus was intentionally brought to North America from Europe as a garden plant for ornamental purposes. Ship ballast has also been cited as a potential vector for the initial introduction. 

It can be spread over long distances by garden planting, and once established in a watershed, it spreads locally by rhizomes, by clonal bulbils, and by fragmentation of the root system via downstream water movement. Bird and water movement of the seeds are other documented pathways (Les 2020). Muskrats reportedly use parts of the plant and contribute to its local spread, though the importance of this particular vector in spreading has not been investigated (Staniforth and Frego 1980). Populations may be spread via the horticulture trade (Lui et al. 2005), and boaters can also transport flowering rush on their equipment. Water and ice movements can easily carry it to new areas of a water body (Proulx 2000).

Status: Butomus umbellatus is a prohibited species in Illinois, Michigan, and Minnesota, and is restricted in Wisconsin (GLPANS 2008). A recent survey of Minnesota Nursery and Landscape Association Members revealed that 80% of respondents were incorrect or unsure of the non-native character of B. umbellatus despite its prohibited status in Minnesota (Peters et al. 2006).

Actively expanding (EPA 2008).

Impact of Introduction:

Summary of species impacts derived from literature review. Click on an icon to find out more...

Ecological	Economic	Human Health	Other

Butomus umbellatus can displace native riparian vegetation, and can be an obstacle to boat traffic (Balgie et al. 2005). Its very wide range of hardiness (zones 3-10) makes it capable of being widely invasive in the United States (IPANE 2001).

Diversity of native plants along the St. Lawrence River was higher at sites with Butomus umbellatus than at sites with Phalaris arundinacea and Phragmites australis (Lavoie et al. 2003). Up to half of the diet of the green-winged teal in Lake Champlain contained Butomus umbellatus plant parts (Martin and Uler 1939). Fish and swimming was impeded in Twin Lakes, Minnesota due to dense stands of Butomus umbellatus (Balgie et al. 2005).

Remarks: The name Butomus umbellatus forma vallisneriifolius (Sagorski) Glück has been used for plants that grow totally submersed or have floating leaves. Field transplant experiments with North American plants (R. L. Stuckey et al. 1990) have demonstrated that the non-flowering submersed form can be converted to a flowering mudflat form, and that flowering terrestrial plants can be transformed into non-flowering submersed ones. Consequently, B. umbellatus f. vallisneriifolius is a deep-water growth form and should have no taxonomic systematic status. A map of Butomus in North America, prepared by R. L. Stuckey (1994), showed that he accepted two species. His map essentially had everything east of Niagara Falls as B. junceus and everything west of the Falls as B. umbellatus. At this time, experts do not accept two species in the genus.

While common in introduced plant populations, Butomus in North America has low genetic variability, likely due to a genetic bottleneck during introduction (Les 2020).

The name, Butomus, comes from the Greek bous tomos, meaning "ox cutting" to reference the unsuitability of the plant for cattle feed (Les 2020).

References: (click for full references)

Anderson, L.C., C.D. Zeis, and S.F. Alam. 1974. Phytogeography and possible origins of Butomus in North America. Bulletin of The Torrey Botanical Club 101(5):292-297. https://doi.org/10.2307/2484875.

Balgie, S., W. Crowell, S. Enger, C. Hamm, G. Montz, N. Proulx, J. Rendall, R. Rezanka, L. Skinner, C. Welling, H. Wolf, and D. Wright. 2005. Invasive Species of Aquatic Plants and Wild Animals in Minnesota, Annual Report for 2004. Minnesota Department of Natural Resources, St Paul, MN. http://fwcb.cfans.umn.edu/courses/NRESExotics3002/Handouts/ExoticSpeciesProg2005anrep.pdf.

Brown, J.S. and C.G. Eckert. 2005. Evolutionary increase in sexual and clonal reproductive capacity during biological invasion in an aquatic plant Butomus umbellatus (Butomaceae). American Journal of Botany 92(3):495—502.

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.

Delisle, F., C. Lavoie, M. Jean, & D. Lachance. 2003. Reconstructing the spread of invasive plants: taking into account biases associated with herbarium specimens. Journal of Biogeography 30:1033—1042.

Eckert, C.G., B. Massonnet, J.J. Thomas. 2000. Variation in sexual and clonal reproduction among introduced populations of flowering rush, Butomus umbellatus (Butomaceae). Canadian Journal of Botany 78(4):437 —446.

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

Global Invasive Species Database. 2005. Available http://www.issg.org/database/species/ecology.asp?si=610&fr=1&sts=sss&lang=EN. Accessed 19 September 2011. 

Great Lakes Panel on Aquatic Nuisance Species (GLPANS). 2008. Prohibited species in the Great Lakes region. Research Coordination Committee, GLPANS. Available: http://www.glc.org/ans/pdf/08-11-26-Great%20Lakes%20Reg%20Species%20List-complete.pdf

Higman, P., and S. Campbell. 2009. Meeting the Challenges of Invasive Plants: A Framework for Action. Michigan Department of Natural Resources Wildlife Division. Lansing, Michigan. 87 pp.

Hroudová, Z. and P. Zákravský. 1993. Ecology of two cytotypes of Butomus umbellatus II. Reproduction, growth and biomass production. Folia Geobotanica and Phytotaxonomica 28(4):413—424.

Hroudová, Z., A. Krahulcová, P. Zákravský, V. Jarolímová. 1996. The biology of Butomus umbellatus in shallow waters with fluctuating water level. Hydrobiologia 340:27—30.

Hudon, C. 2004. Shift in wetland plant composition and biomass following low-level episodes in the St. Lawrence River: looking into the future. Canadian Journal of Fisheries and Aquatic Sciences 61(4):603—617.

Invasive Plant Atlas of New England (IPANE). 2009. University of Connecticut. Available http://www.eddmaps.org/ipane/. Accessed 5 April 2012.

Jensen, D. 2011. Flowering rush (Butomus umbellatus). Minnesota Sea Grant. Available http://www.seagrant.umn.edu/ais/floweringrush. Accessed 20 March 2012.

Lavoie, C., M. Jean, F. Delisle, and G. Létourneau. 2003. Exotic plant species of the St Lawrence River wetlands: a spatial and historical analysis Journal of Biogeography 30: 537—549.

Les, D.H., and L.J. Mehrhoff. 1999. Introduction of Nonindigenous Aquatic Vascular Plants in Southern New England: A Historical Perspective. Biological Invasions 1(2): 281-300.

Les, D.H. 2020. Aquatic monocotyledons of North America: ecology, life history, and systematics. CRC Press, Boca Raton, FL.

Lui, K. 2001. Genetic causes & consequences of variation in sexual fertility amoung introduced population of clonal aquatic plant Butomus umbellatus (Butomaceae). Master of Science Thesis. Queen's University Kinsgton, Ontario, Canada. 126 pp.

Lui, K., F.L. Thompson, and C.G. Eckert. 2005. Causes and consequences of extreme variation in reproductive strategy and vegetative growth among invasive populations of a clonal aquatic plant, Butomus umbellatus L. (Butomaceae). Biological Invasions 7:427—444.

Manitoba Purple Loosestrife Project (MPLP). 2006. Flowering rush, an invasive plant found in Manitoba: Butomus umbellatus. Invasive Species Council of Manitoba. Available http://www.invasivespeciesmanitoba.com/site/uploads/pdf/fs_flowrush.pdf. Accessed 2011.

Marsden, J.E., and M. Hauser. 2009. Exotic species in Lake Champlain. Journal of Great Lakes Research 35: 250—265.

Martin, A.C., and F.M. Uhler. 1939. Food of game ducks in the United States and Canada. Volume 634. U.S. Department of Agriculture, Washington DC, US. https://books.google.com/books?hl=en&lr=&id=0cBRAAAAMAAJ&oi=fnd&pg=PA2&dq=Food+of+game+ducks+in+the+United+States&ots=iw-dsl_a8k&sig=L042dr9i3hhy6QGGwCXBKJahDuw#v=onepage&q&f=false.

Minnesota Department of Natural Resources (MNDNR). 2012. Flowering rush (Butomus umbellatus). Available http://www.dnr.state.mn.us/invasives/terrestrialplants/herbaceous/floweringrush.html. Accessed 20 March 2012.

New York State Department of Environmental Conservation (NYDEC). 2011. Interim Invasive Species Plant List. Available http://www.dec.ny.gov/animals/65408.html. Accessed 20 March 2012.

Ohio Division of Natural Areas and Preserves. 2000. Ohio's Invasive Plant Species. The Nature Conservancy, Columbus, Ohio. 2 pp.

Özbay, H. and A. Alim. 2009. Antimicrobial activity of some water plants from the northeastern Anatolian region of Turkey. Molecules 14:321—328.

Parkinson, H., J. Mangold, V. Dupuis, and P. Rice. 2010. Biology, Ecology and Management of flowering rush (Butomus umbellatus). The U.S. Department of Agriculture, Montana State University Extension. Bozeman, MT. 12 pp.

Peters, W.L., M. Hockenberry Meyer, and N.O. Anderson. 2006. Minnesota horticultural industry survey on invasive plants. Euphytica 148:75—86.

Plants For A Future. 2004. Butomus umbellatus. Available http://www.pfaf.org

Proulx, N. 2000. Exotic Flowering Rush. Minnesota Sea Grant: Regents of the University of Minnesota. Available http://www.seagrant.umn.edu/ais/floweringrush. Accessed 5 March 2012.

Rice, P. and V. Dupuis. 2009. Flowering rush: an invasive aquatic macrophyte infesting the headwaters of the Columbia River system. Center for Invasive Plant Management (CIPM), Montana State University, Bozeman, MT. 11 pp.

Seizer, M. 2009. The Michigan Department of Environmental Quality Biennial Remedial Action Plan Update for the River Rasion Area of Concern. Water Bureau, Aquatic Nuisance Control & Remedial Action Unit: Michigan DEQ, Lansing, MI. 15 pp.

Staniforth, R.J. and K.A. Frego. 1980. Flowering rush (Butomus umbellatus) in the Canadian prairies. Canadian Field-Naturalist 94(3):333—336.

Stuckey, R.L. 1968. Distributional history of Butomus umbellatus (flowering rush) in the western Lake Erie and Lake St. Clair region. Michigan Botanist 7(3):134-142. https://www.biodiversitylibrary.org/item/262400.

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 33:705—721.

United States Department of Agriculture National Resources Conservation Service (USDA, NRCS). 2008. The PLANTS Database. National Plant Data Center, Baton Rouge, LA. Available http:// http://plants.usda.gov. Accessed  5 August 2008.

White, D., E. Haber, and C. Keddy. 1993. Invasive plants of natural habitats in Canada: an integrated review of wetland and upland species and legislation governing their control. Canadian Wildlife Service, Environment Canada, Ottawa, Ontario.

Other Resources:
Butomus umbellatus in America by Earl L. Core (1941)

US Fish and Wildlife Service Ecological Risk Screening Summary for Butomus umbellatus

Author: Cao, L., L. Berent, and A. Fusaro

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.