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.

Rorippa sylvestris
Rorippa sylvestris

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Rorippa sylvestris (L.) Besser

Common name: keek

Synonyms and Other Names: Radicula sylvestris; Keek; Yellow fieldcress

Taxonomy: available through www.itis.govITIS logo


Stems - Herbaceous, erect, from rhizomes, glabrous, green or becoming purple in the strong sun, ribbed, to +/-35cm tall, branching (Missouri Flora Web).

Leaves - Alternate, petiolate, deeply pinnatifid. Basal leaves to -10cm long, 2-2.5cm broad, with +/-6 main divisions per side. Cauline leaves similar but reduced. All leaves glabrous or with very few short hairs. Divisions of the leaves toothed. Upper leaves with thinner and fewer divisions than the lower. Tissue connecting the divisions of the leaves 0.2-0.3mm broad (Missouri Flora Web).

Inflorescence - Terminal and axillary racemes to +10cm long. Axis glabrous. Pedicels to 4mm long in flower, expanding to +/-1cm long in fruit, glabrous. Inflorescence compact in flower, quickly expanding. Siliques to 1cm long, 1mm in diameter, cylindric but slightly compressed, glabrous, with a beak to 1mm long (Missouri Flora Web).

Flowers - Petals 4, distinct, spatulate, yellow, glabrous, to +4mm long, 1.5mm broad, rounded at the apex. Stamens 6, erect, 4 larger and 2 smaller. Filaments yellow, glabrous, to 3mm long. Anthers yellow, 1mm long. Ovary cylindric, green-yellow, glabrous, 2mm long in flower, superior. Style .5mm long. Stigmas globose-capitate, .7mm broad. Sepals 4, distinct, yellow, erect to spreading, cupped, mostly glabrous but often with a few hairs at the apex externally, entire, 2-2.5mm long, to 1mm broad, subulate (Missouri Flora Web).

Size: maximum height: 0.7 feet.

Native Range: USDA ARS (National Genetic Resources Program) cites native range as western Asia, Caucasus, Northern Europe, Middle Europe, east Europe, East Europe, Southeastern Europe, and Southwestern Europe.

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

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Rorippa sylvestris are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
AL188320082Mobile-Tensaw; South Atlantic-Gulf Region
AK200620061Upper Kenai Peninsula
AZ200820081Lower Colorado Region
CA200820081California Region
CT200820081New England Region
DC200820081Middle Potomac-Anacostia-Occoquan
ID200820081Pacific Northwest Region
IL1878201336Apple-Plum; Bear-Wyaconda; Big Muddy; Cache; Chicago; Copperas-Duck; Des Plaines; Flint-Henderson; Iroquois; Kankakee; La Moine; Little Wabash; Lower Illinois; Lower Illinois; Lower Illinois-Lake Chautauqua; Lower Illinois-Senachwine Lake; Lower Ohio; Lower Ohio-Bay; Lower Rock; Lower Sangamon; Lower Wabash; Middle Wabash-Busseron; Pike-Root; Rock; Saline; Salt; South Fork Sangamon; Upper Illinois; Upper Mississippi; Upper Mississippi Region; Upper Mississippi-Cape Girardeau; Upper Mississippi-Meramec; Upper Mississippi-Skunk-Wapsipinicon; Upper Sangamon; Vermilion; Wabash
IN1973200823Blue-Sinking; Driftwood; Eel; Kankakee; Little Calumet-Galien; Lower East Fork White; Lower Ohio-Little Pigeon; Lower White; Middle Ohio-Laughery; Middle Wabash-Busseron; Middle Wabash-Little Vermilion; Silver-Little Kentucky; St. Joseph; St. Marys; Sugar; Tippecanoe; Upper Illinois; Upper Maumee; Upper Wabash; Upper White; Vermilion; Wabash; Wildcat
ME200820081New England Region
MD200820081Mid Atlantic Region
MA200820081New England Region
MI1891201811Betsie-Platte; Boardman-Charlevoix; Detroit; Great Lakes Region; Lower Grand; Saginaw; Southeastern Lake Michigan; St. Clair; St. Clair-Detroit; Upper Grand; Western Lake Erie
MN195520087Beaver-Lester; Clearwater-Elk; Lower Minnesota; South Fork Crow; St. Louis; Twin Cities; Upper Mississippi-Crow-Rum
MO200820161Lower Missouri-Moreau
NE200820081Missouri Region
NH200820081New England
NJ200820081Mid-Atlantic Region
NY1884200823Bronx; Cattaraugus; Conewango; Eastern Lake Erie; Great Lakes Region; Lake Ontario; Long Island; Lower Genesee; Lower Hudson; Middle Hudson; Mohawk; Oneida; Oswego; Owego-Wappasening; Richelieu; Schoharie; Seneca; Southern Long Island; St. Lawrence; Upper Delaware; Upper Hudson; Upper Susquehanna; Upper Susquehanna
OH1927200829Auglaize; Cedar-Portage; Cuyahoga; Hocking; Lake Erie; Little Miami; Little Muskingum-Middle Island; Lower Great Miami, Indiana, Ohio; Lower Maumee; Lower Scioto; Mahoning; Middle Ohio; Middle Ohio-LittleMiami; Middle Ohio-Raccoon; Mohican; Muskingum; Ohio Brush-Whiteoak; Ottawa-Stony; Paint; Sandusky; Southern Lake Erie; Tuscarawas; Upper Ohio; Upper Ohio-Beaver; Upper Ohio-Wheeling; Upper Scioto; Walhonding; Western Lake Erie; Wills
OR193820084Middle Columbia-Hood; Pacific Northwest Region; Upper Willamette; Wallowa
PA1818200825Allegheny; Delaware; Lake Erie; Lehigh; Lower Allegheny; Lower Delaware; Lower Juniata; Lower Monongahela; Lower Susquehanna; Lower Susquehanna; Lower Susquehanna-Penns; Lower Susquehanna-Swatara; Lower West Branch Susquehanna; Mid Atlantic Region; Middle Allegheny-Tionesta; Middle Delaware-Mongaup-Brodhead; Monongahela; Schuylkill; Upper Delaware; Upper Juniata; Upper Ohio; Upper Ohio-Beaver; Upper Susquehanna; Upper Susquehanna-Lackawanna; Upper Susquehanna-Tunkhannock
RI200820081New England Region
WA200820081Pacific Northwest Region
WI1927200818Buffalo-Whitewater; Lake Dubay; Lake Superior; Lower St. Croix; Lower Wisconsin; Manitowoc-Sheboygan; Northwestern Lake Michigan; Pecatonica; Pike-Root; Rock; Rush-Vermillion; Southwestern Lake Michigan; St. Croix; Upper Fox; Upper Fox; Upper Mississippi-Maquoketa-Plum; Upper Rock; Upper Wisconsin

Table last updated 4/20/2024

† Populations may not be currently present.

* HUCs are not listed for states where the observation(s) cannot be approximated to a HUC (e.g. state centroids or Canadian provinces).

Ecology: Habitats are disturbed wetlands, including muddy or grassy borders of ditches, soggy meadows in floodplain areas, and poorly drained areas along railroads. Flowering from May-September.

Means of Introduction: Solid ballast. Tiny seeds can likely float on water or blow about in the wind. R. sylvestris is believed to spread rapidly at times of fast creek flow in autumn and winter in South Australia when rhizomes can fragment and spread downstream (Woldendorp and Bomford, 2004). In the United States, Emore (1998) has documented vegetative material (rhizomes) of the weed being shipped within the roots of herbaceous ornamentals, such as lilies, daylilies, and hosta.

Status: Established.

Impact of Introduction: Considered a noxious weed in parts of the United States. It can form dense, tangled masses of stems and intertwining rhizomes floating in water or creeping over mud; rooted at several points, which may be several yards long (NatureServe. 2008). This species does not appear to have highly significant impacts, although it is expanding and becoming more noxious in the northeast (e.g. Hudson River basin) as well as in the Great Lakes, where it is considered an invasive aquatic species in some areas. In California and the Pacific Northwest, this species has recently emerged as an invasive pest with potential to invade natural systems through creeks when rhizome pieces (which can occur at depths up to 3 feet) fragment (Elmore, 1998).

In Germany, native Rorippa sylvestris hybridizes with non-native R. austriaca, forming Rorippa x armoracioides hybrids which appear to be more competitive/invasive than either of the parent species. Although both parents are present in the US and are likely to hybridize where they form contact zones, this potentially invasive hybrid has not yet been confirmed present (NatureServe. 2008).

Remarks: Unlike many other members of the mustard family, the yellow cresses are largely restricted to wetland habitats.

References: (click for full references)

Bleeker, W. 2003. Hybridization and Rorippa austriaca (Brassicaceae) invasion in Germany. Molecular Ecology, 12: 1831-1841.  

Dorn, R.D. 1984. Vascular plants of Montana. Mountain West Publishers, Cheyenne.  

Elmore, C. 1998. New weed in California: creeping field cress. IPM Notes, 3(2): unpaginated.  

Elmore, C.L., L. Kuhns and T. Harpster.  1996.  Rorippa sylvestris, creeping fieldcress: A threat to production ornamentals and its control.  Hort Science 31(4)578.

Eilers, L.J., and D.M. Roosa. 1991. The vascular plants of Iowa. University of Iowa Press, Iowa City.

Mills, E.L., M.D. Scheuerell, J.T. Carlton, and D.L. Strayer. 1997. Biological invasions in the Hudson River basin. New York State Museum Circular, 57: 1-51.  

NC State.  2012.  Yellow fieldcress.  Accessed 12/9/13.  http://www.cals.ncsu.edu/plantbiology/ncsc/containerWeeds/Rorippa_sylvestris.htm

Stuckey, R.L. 1972. Taxonomy and distribution of the genus Rorippa (Cruciferae) in North America. Sida 4(4): 79-430.  

Thomas, R.D., and C.M. Allen. 1997. Atlas of the vascular flora of Louisiana, vols. 1-3 (Plus updates). Louisiana Department of Wildlife and Fisheries. Natural Heritage Program, Baton Rouge.  

Woldendorp, G., and M. Bomford. 2004. Weed eradication. Strategies, timeframes and costs. BRS Publication Sales, Common wealth of Australia: Camberra ACT Australia. 30 pp.

Yamane, A., H. Nishimura, and J. Mizutani. 1992. Allelopathy of yellow fieldcress (Rorippa sylvestris): Identification and characterization of phytotoxic constituents. Journal of Chemical Ecology 18(5):683-691.

Other Resources:

NatureServe. 2008. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.0. NatureServe, Arlington, Virginia. Available http://www.natureserve.org/explorer. (Accessed:  July 24, 2008).  

USDA, NRCS. 2008. The PLANTS Database. USDA Natural Resources Conservation Service (USDA, NRCS). National Plant Data Center, Baton Rouge, Louisiana 70874-4490 USA. Available online: http://plants.usda.gov.  

Missouri Flora Web. http://www.missouriplants.com/Yellowalt/Rorippa_sylvestris_page.html  


Author: Cao, L., and R. Sturtevant

Revision Date: 8/9/2019

Citation Information:
Cao, L., and R. Sturtevant, 2024, Rorippa sylvestris (L.) Besser: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=2682, Revision Date: 8/9/2019, Access Date: 4/20/2024

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.


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Citation information: U.S. Geological Survey. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [4/20/2024].

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