Marsh yellowcress [Rorippa palustris (L.) Besser][RORIS] Photographs

Austrian fieldcress [Rorippa austriaca (Crantz) Besser][RORAU][CDFA list: B] Photographs Map of Distribution

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marsh yellowcress: marshcress, common yellow-cress, yellow water cress, Rorippa islandica (Oeder) Borbas, Nasturtium terrestre (Withering) R. Brown, and many others. A complete synonymy for this species is complicated and beyond the scope of this publication.

Austrian fieldcress: Nasturtium austriacum Crantz, Radicula austriaca (Crantz) Small

GENERAL DESCRIPTION:Mustard-like plants with yellow flowers that typically grow on wet soils.

marsh yellowcress: Widespread native annual, biennial, or short-lived perennial, to 1.4 m tall. This species consists of a highly variable complex of subspecies and varieties. Two varieties differing in hairiness and fruit length occur in California. Variety occidentalis (S. Watson) Rollins is glabrous, has longer fruits, and is much more common than var. hispida (Desv.) Rydb. Marsh yellowcress has been called R. islandica. However, R. islandica is a separate species not known to occur in North America. Marsh yellowcress is usually a desirable component of natural communities, but it can be a pest in orchards, vineyards, irrigated crops, and drainage areas.

Austrian fieldcress: Competitive noxious perennial with aggressive creeping roots and persistent stems to 1 m tall. Patches spread primarily by creeping roots. Introduced from Europe.

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SEEDLINGS:Cotyledons oval, 2-6 mm long, ~ 1-2 mm wide, on stalks about equal in length, often withered by the 4-leaf stage. Early rosette leaves alternate, often at least 4 times larger than the cotyledons, ovate, on stalks equal to or longer than the blades.

marsh yellowcress: Early rosette leaves +/- succulent, mostly glabrous. Margins entire to shallow-wavy or angled (repand to sinuate), with glands or short thick hairs on the apices of the angles. Later rosette leaves deeply pinnate-lobed.

Austrian fieldcress: Rosette leaves +/- covered with short unicellular hairs. Margins of early leaves entire to irregularly toothed. Later rosette leaves oblong to oblanceolate, unequally toothed (serrate to dentate) but not lobed.

MATURE PLANT:Exist as basal rosettes until flowering stems develop in spring. Stem leaves alternate.

marsh yellowcress: Stems erect, typically with 1 dominant stem from the base, sometimes branched. Leaves variable, irregularly toothed to deeply pinnate-lobed, 5-14(30) cm long, sessile (sometimes clasping stem) or short-stalked, glabrous (var. occidentalis) or covered with short hairs (var. hispida).

Austrian fieldcress: Stems ascending to nearly erect, branched near the top. Leaves dull bluish-green, glabrous, narrowly oblong to oblanceolate, 3-10 cm long, entire to unequally toothed (dentate to serrate). Upper stem leaves narrow to a stalk-like base that clasps the stem.

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marsh yellowcress: Taproot slender, pale yellowish, with fibrous secondary roots. Crowns and taproots can produce new shoots.

Austrian fieldcress: Taproots deep, thick, fleshy, resemble those of horseradish [Armoracia rusticana P. Gaertner, Meyer & Scherb.] with fine fibrous roots and extensive creeping lateral roots that produce new shoots. Buried root fragments can produce new plants.

FLOWERS:Yellow, 4-petaled, in short terminal and axillary racemes. Stamens 6. Styles persistent.

marsh yellowcress: April-September. Petals 1-3.5 mm long, +/- equal to or shorter than sepals.

Austrian fieldcress: June-August. Petals 3-5 mm long, longer than sepals. Sepals 1-2 mm long.

FRUITS and SEEDS:Silicles (specialized capsules) typically more than 2 mm wide, 2-valved, on spreading to ascending stalks, open from the base to release seed. Seeds 0-several per valve, flattened, +/- oval to heart-shaped, 0.5-1 mm long, orange-brown, covered with minute bumps (high magnification).

marsh yellowcress: Silicles +/- ovoid and 2-6 mm long (var. hispida) to oblong and 7-15 mm long (var. occidentalis), often curved upwards, on stalks 2-14 mm long. Styles to 1 mm long.

Austrian fieldcress: Silicles +/- ovoid, ~ 3 mm long. Lower stalks 7-15 mm long. Styles ~ 2-3 mm long. Viable seed rarely produced.

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marsh yellowcress: Stream banks, marshy areas, often with roots immersed, moist depressions, ditches, irrigation canals, orchards, vineyards, irrigated crops. Grows best on fertile, wet to moist soils, but tolerates a wide range of soil conditions.

Austrian fieldcress: Disturbed and cultivated sites, roadsides, fields, especially hay fields, mud flats. Typically inhabits areas where the soil is wet from 6-8 months during the year.


marsh yellowcress: Throughout California (var. occidentalis) and Modoc Plateau (var. hispida). To 2000 m (6560 ft). To Arkansas, New Mexico, Mexico.

Austrian fieldcress: Modoc Plateau, 1200-2000 m (3950-6560 ft). To Canada, Eastern U.S.

PROPAGATION/PHENOLOGY:Seeds disperse with water, in mud, harvested crops, on feet, fur, or feathers of animals, clothes and shoes of people, and agricultural equipment.

marsh yellowcress: Reproduces by seed, sometimes from roots or crowns. Seed germinates summer, fall, or winter.

Austrian fieldcress: Reproduces vegetatively from creeping roots, rarely by seed. Stems can develop adventitious roots in water.

MANAGEMENT FAVORING/DISCOURAGING SURVIVAL:Improving drainage of wet soils, repeated cultivation, and crop rotation can help control troublesome infestations in agricultural fields.

SIMILAR SPECIES:Yellow fieldcress [Rorippa sylvestris (L.) Bess.][RORSY][CDFA list: Q] is a glabrous European perennial with aggressive creeping roots similar to those of Austrian fieldcress. Unlike Austrian fieldcress and marsh yellowcress, yellow fieldcress has linear siliques 10-25 mm long and ~1.5 mm wide and pinnately dissected leaves that appear nearly compound. Yellow fieldcress has recently been found (1997-98) in a few California nurseries and has become established in Monterey County. Like Austrian fieldcress, yellow fieldcress spreads vegetatively from creeping roots and has not been reported to produce viable seed in California.

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Biology and Control: Austrian fieldcress is a persistent perennial in the mustard family. It is native to Russia and Eastern Europe, but was introduced to the United States in 1910. It was soon discovered in Modoc County, California along the Pit River. By 1935, the infestation covered over 25,000 acres. It has been found in Washington and Nevada, but neither Oregon nor Idaho has reported it. No other infestations have been reported in California.
Austrian fieldcress reproduces by seeds and asexually by creeping roots. However, seed production appears to be limited as few pods develop to maturity. The roots are extremely persistent and are likely the primary means of spread. New plants may be propagated from small root fragments. Additionally, stems readily form adventitious roots when lying in water and may produce new plants if detached. New plants primarily establish in disturbed areas and are favored by soils that remain wet six to eight months each year. These factors may suggest the potential for invasion along rivers when flooding occurs. When established, it competes vigorously and may threaten native species in riparian corridors.
Efforts to control the Modoc infestation were undertaken, beginning in 1935. These included draining the infested area and implementing an agricultural cropping program. By 1944, the infestation was reduced from 25,000 acres to about 40 acres. Subsequent applications of 2,4-D during the late 1940's resulted in almost complete eradication of the weed. This was one of the most successful eradication programs in California. Surveys conducted in 1964 and 1974 indicated little to no spread of the weed in the area and no movement down the Pit River drainage system. Any new infestations discovered should be immediately reported to the County Agricultural Commissioner.
In agricultural areas, Austrian fieldcress may persist in irrigated pastures and hay fields, and contaminated hay can be a significant means of spread. Rotating to a cropping system that uses less water and allows for intensive cultivation and herbicides is probably the most effective way to control Austrian fieldcress. However, it is critical to clean tillage equipment thoroughly after working in infested areas. Effective herbicides include 2,4-D and glyphosate. Both herbicides are also registered for use in aquatic settings and can be spot applied to infestations in riparian areas.

Hickman, J. C. 1993. The Jepson Manual. Higher Plants of California. Berkeley, CA: University of California Press.
Roche, C. T. 1992. Austrian fieldcress (Rorippa austriaca). Pacific Northwest Cooperative Extension Publication 411:1-2.
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