florida Early Detection Network




Rorripa nasturtium-aquaticum (L.) Hayek


Mustard family


Rorippa nasturtium-aquaticum





Synonyms: Nasturtium nasturtium-aquaticum (L.) Karsten, Nasturtium officinale Ait. f., Sisymbrium nasturtium-aquaticum L.


Botanical Glossary

Rorippa nasturium-aquaticum is a perennial plant that can have submersed stems, partly floating stems, or grow prostrate on mud. The stems root from the nodes. The leaves are comprised of 3-9 segments. The terminal segment is larger than the lateral ones. The leaf segments can be obtuse, ovate or oval in shape, and the terminal one can be nearly orbicular. The small, white flowers are borne in elongating racemes and measure about 5 mm (0.2 in.) wide, with the petals twice as long as the sepals. The pod-like fruits, called siliques, are slender, and measure 1-1.5 cm (0.4-0.6 in.) long and about 2 mm (0.08 in.) wide. They are borne on pedicels measuring 6-15 mm (0.25-0.6 in.) long. The fruits have a 1 mm (0.04 in.) long tip. The coarsely reticulate seeds within the pod are small and are contained in two rows. The seeds of Rorippa nasturium-aquaticum have 25 to 50 reticulations on their surface. This plant can be in bloom all summer. Page References Bailey 447, Crow & Hellquist 153, Fernald 1716, Gleason & Cronquist 193, Holmgren 177, Magee & Ahles 549, Newcomb 148, Peterson & McKenny 84. See reference section below for full citations.


Rorippa microphylla (Boenn. ex Reichenb.) Hyl. ex A.& D. Love (Onerow yellowcress) Rorippa nasturtium-aquaticum and R. microphylla are very difficult to distinguish from each other in the field. Ecologically, they behave similarly. This comparison chart shows several differences in characters of the two species, but the most reliable character is the difference in reticulations on the seeds. Mature seeds are necessary for accurate identification.


Rorippa nasturtium-aquaticum reproduces mainly by means of seed, though plant fragments can give rise to new plants locally. Both seeds and segments are dispersed by water.


Rorripa nasturium-aquaticum is native to North Africa, the Middle East, and Europe from Ireland to Italy and Portugal to Turkey. This plant has been found in all of the states United States except North Dakota and Hawaii, and is also reported from Puerto Rico and the Virgin Islands.


In 1831, Rorippa nasturtium-aquaticum was first reported from southern New England near Yale University in New Haven, Connecticut. The first specimen of this plant in the United States was collected in 1841 in Niagra, New York. It was described by Gray in 1857 as a rare escape from cultivation. Many people feel that it has been in this country since the middle of the 18th century. However, it is likely that it did not become established until the mid 1800's, since this is when records and specimens were collected. By the end of the 1800's, this plant made its way all the way to the west coast. In 1900, it has been reported from 17 states in the United States, including the New England states of Connecticut, Massachusetts and Vermont.


Aquatic, Lake or Pond, River or Stream. Rorippa nasturtium-aquaticum is often found in coldwater brooks, seeps and springs, but can be found in other bodies of water as well.


Many people do not acknowledge Rorippa nasturtium-aquaticum as a possible invasive because they consider it to be native. However, in 1899 near Concord Massachusetts, this plant was so abundant that it was removed in cartloads to prevent the stream from flooding the nearby area. This plant also has a rapid growth rate, and when grown commercially, can be harvested within only 30 days. Right after the seeds fall from the plant, they have a 97% germination rate. They also maintain a relatively high viability rate (68%) after five years, which could make this plant difficult to control.


Documentation required: A mounted snippet of the plant with fruits. Best time for documentation: Late spring, summer, fall.


Integrated Taxonomic Information System - Has general taxonomic information about the species.

The PLANTS Database - General information and map

Connecticut Botanical Society - Images


Al-Shehbaz, I.A. and R.C. Rollins. 1988. A reconsideration of Cardamine curvisilqua and C. gambellii as species of Rorippa (Cruciferae). Journal of the Arnold Arboretum 69: 65-71

Bailey, L.H. 1949. Manual of Cultivated Plants. Macmillan, New York.

Brown, N.L. and A. Brown. 1970. An Illustrated Flora of the Northeastern United States vol. 2. Dover Publications Inc., New York.

Crow, G.E. and C.B. Hellquist. 2000. Aquatic and Wetland Plants of Northeastern North America. Vol 1. University of Wisconsin Press, Madison.

Fernald, M.L. 1950. Gray's Manual of Botany 8th ed. American Book Co., Boston.

Gleason, H.A. and A.C. Cronquist. 1991. Manual of Vascular Plants of the Northeastern United States and Adjacent Canada. 2nd ed. New York Botanical Garden, Bronx, New York.

Gray, A. 1857. Manual of the Botany of the Northern United States, Revised edn. Ivison and Phinney, New York, 631 pp.

Green, P.S. 1962. Watercress in the New World. Rhodora 64: 32-43.

Henry, C.P. and C. Amoros. 1996. Are the banks a source of recolonization after disturbance: An experiment on aquatic vegetation in a former channel of the Rhone river. Hydrobiologia 330(2): 151-162.

Holmgren, N.H. 1998. Illustrated Companion to Gleason and Cronquist's Manual. New York Botanical Garden, Bronx, New York.

Ives E., W. Tully, M.C. Leavenworth. 1831. Catalogue of the phenogamous plants and the ferns growing without cultivation, within five miles of Yale College, Ct. Hezekiah Howe, New Haven, Connecticut, 38 pp.

Kerfoot, W.C., R.M. Newman and Z. Hanscom. 1998. Snail reaction to watercress leaf tissues: reinterpretation of a mutualistic 'alarm' hypothesis. Freshwater Biology 40(2): 201-213.

Les, D.H. and L.J. Mehrhoff. 1999. Introduction of nonindigenous aquatic vascular plants in southern New England: a historical perspective. Biological Invasions 1:281-300.

Magee, D.W and H.E. Ahles. 1999. Flora of the Northeast. University of Massachusetts Press, Amherst.

Newcomb, N. 1977. Newcomb's Wildflower Guide. Little Brown, Boston.

Newman, R.M., W.C. Kerfoot and Z. Hanscom. 1996. Watercress allelochemical defends high-nitrogen foliage against consumption: Effects on freshwater invertebrate herbivores. Ecology 77(8): 2312-2323.

Peterson, R.T. and M. McKenny. 1968. A field Guide to Wildflowers of Northeastern and North-central North America. Houghton Mifflin, Boston.

Philosophhadas, S., S. Meir and N. Aharoni. 1994. Role of ethylene in senescence of watercress leaves. Physiologia Plantarum 90(3): 553-559.

Selker, J.M.L. and R.F. Lyndon. 1996. Leaf initiation and de novo pattern formation in the absence of an apical meristem and pre-existing patterned leaves in watercress (Nasturtium officinale) axillary explants. Canadian Journal of Botany-Revue Canadienne De Botanique 74(4): 625-641.

USDA, NRCS. 2001. The PLANTS Database, Version 3.1. (//plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.