Marsh yellowcress [Rorippa
palustris (L.) Besser][RORIS] Photographs
Austrian fieldcress [Rorippa
austriaca (Crantz) Besser][RORAU][CDFA list: B] Photographs
Map of Distribution
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
Austrian fieldcress: Nasturtium
austriacum Crantz, Radicula austriaca (Crantz) Small
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
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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.
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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and UNDERGROUND STRUCTURES:
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.
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
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
marsh yellowcress: Reproduces
by seed, sometimes from roots or crowns. Seed germinates summer, fall,
Austrian fieldcress: Reproduces
vegetatively from creeping roots, rarely by seed. Stems can develop adventitious
roots in water.
drainage of wet soils, repeated cultivation, and crop rotation can help control
troublesome infestations in agricultural fields.
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
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.