Weed Information: Rorippa palustris (yellowcress, marsh)
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Rorippa palustris (yellowcress, marsh)

Family: Brassicaceae

Description

Generally in water, although sometimes these sites drying late in the season. The fruits can be curved or straight. The leaves are pinnately lobed, the tiny, yellow flowers often brownish on the outside. The stems of the fruits are usually at least as long as the fruits themselves. For the purposes of this program we will consider this species to be the same as Rorippa islandica, however, this is a matter of controversy in the scientific community.

Characteristics

Flower Color
  • Yellow
Inflorescence Type (How the flowers are arranged on the plant)
  • Axillary racemes
  • Terminal raceme
Number of Petals
  • 4 petals
Petal Separation
  • Completely free to base
Petal Tip
  • Rounded
Flower Symmetry
  • Flowers regular
Flower Length (Head length in the Asteraceae)
  • 2 mm (.08 inch)
  • 3 mm (.12 inch)
Flower Width (Head width in the Asteraceae)
  • 2 mm (.08 inch)
  • 3 mm (.12 inch)
Number of Sepals
  • 4 sepals
Sepal Separation
  • Completely free to base
Sepal Tip
  • Pointed
Flower Sex
  • Bisexual (perfect)
Number of Styles
  • 1 style
Number of Stamens
  • 6 stamens
Stamens Attached to the Petals
  • Stamens NOT attached to the petals
Stamens Connate (united)
  • Filaments or anthers NOT united

Carpel Separation
  • Carpels united (or one)
Number of Carpels
  • 2 carpels
Ovary Position
  • Superior (hypogynous)
Fruit Type
  • Capsule, 2-celled
Fruit Length at Maturity
  • 6 mm (.24 inch)
  • 7 mm (.28 inch)
  • 8 mm (.32 inch)
  • 9 mm (.36 inch)
  • 1.0 cm (.40 inch)
  • 1.5 cm (.60 inch)
Fruit Width at Maturity
  • 2 mm (.08 inch)
  • 3 mm (.12 inch)
  • 4 mm (.16 inch)
Burs
  • Fruit or seed NOT bur-like

Leaf Arrangement
  • Alternate
Leaf Type
  • Simple (including lobed leaves)
Stipules
  • Lacking
Tendrils
  • Tendrils absent
Venation
  • Pinnate
Petiole (leaf stem) Blade Ratio
  • Petiole absent (leaf sessile)
  • Petiole < 25% total length
Leaf Length (blade PLUS petiole)
  • 4 - 10 cm (1.60 - 4.0 inches)
  • 1 - 2 dm (4.0 - 8.0 inches)
Leaf Width
  • 5 - 10 mm (.20 - .40 inch)
  • 1 - 2 cm (.40 - .80 inch)
  • 2 - 4 cm (.80 - 1.6 inches)
Leaf Shape (simple leaves only)
  • Lanceolate
  • Pinnately lobed
Leaf or Leaflet Margin
  • Dentate
  • Lobed
Leaf or Leaflet Blade Base
  • Acute (cuneate)
Leaf or Leaflet Tip
  • Acute
  • Rounded (obtuse)
Leaf or Leaflet Blade Surface
  • Glabrous (NO hairs)
Succulence
  • Not succulent

Milky Juice
  • Juice NOT milky (watery)
Woodiness
  • Herbaceous
Spines or Thorns
  • Spines or Thorns ABSENT
Aromatic (vegetative structures)
  • Not aromatic
Life Cycle
  • Annual
  • Biennial
  • Perennial
Growth Habit (while flowering)
  • Spreading ascending
  • Erect, columnar (narrow)
  • Erect, spherical (bushy)
Plant Height at Maturity
  • 2 - 4 dm (8.0 - 16.0 inches)
  • 4 - 6 dm (1.3 - 2.0 feet)
  • 6 - 8 dm (2.0 - 2.6 feet)
Wind Dissemination
  • Not wind disseminated
Moisture Regime
  • Aquatic
  • Semi-aquatic
Chlorophyll
  • Present

Stem Cross Section
  • Round
Flowering Stem Leaves
  • Stem uniformly leafy
Main Stem Branches
  • Main stem branched

Root or Vegetative Propagule
  • Fibrous

US State
  • Alabama
  • Arkansas
  • Connecticut
  • Delaware
  • Florida
  • Georgia
  • Illinois
  • Kansas
  • Kentucky
  • Louisiana
  • Massachusetts
  • Maine
  • Michigan
  • Missouri
  • Mississippi
  • North Carolina
  • New Hampshire
  • New Jersey
  • New York
  • Ohio
  • Pennsylvania
  • South Carolina
  • Tennessee
  • Texas
  • Virginia
  • Wisconsin
  • West Virginia
  • Indiana
  • Maryland
  • Rhode Island
  • Vermont
  • Alaska
  • Arizona
  • California
  • Colorado
  • Iowa
  • Idaho
  • Minnesota
  • Montana
  • North Dakota
  • New Mexico
  • Nevada
  • Oklahoma
  • Oregon
  • South Dakota
  • Utah
  • Washington
  • Wyoming
  • Nebraska
Canadian Province or Territory
  • British Columbia
  • New Brunswick
  • Nova Scotia
  • Ontario
  • Prince Edward Island
  • Quebec
  • Alberta
  • Manitoba
  • Newfoundland
  • Saskatchewan
  • Yukon
  • Nunavut
  • Northwest Territory
Other
  • Puerto Rico
  • Virgin Islands
  • District of Columbia
  • St. Pierre and Miquelon
  • Labrador

  • California Growers Weed Identification Handbook, 1968 - 1998 University of California Publication # 4030-1, See page: 205
  • Common Weeds of the Canadian Prairies, 1963 (Cat# A53-1136-1) See page: 55
  • Field Guide To The Common Weeds Of Kansas, 1983 (ISBN 0-7006-0233-X) See page: 50
  • How to Know the Weeds, 1972, (ISBN# 0-697-04880-2) See page: 90
  • Identification Guide to the Weeds of Quebec, 1999 (ISBN# 2-89457-174-7) See page: 100
  • Manual of Ohio Weeds, 1931 Ohio Ag. Exp. Station Bull. # 475, See page: 38
  • Ontario Weeds, 1992 Agdex 640, Publication #505 See page: 101
  • Weeds, 1955 (1980) Walter Conrad Muenscher, ISBN# 0-8014-1266-8 See page: 254, 255
  • Weeds of California, 1970, State of California Publications and Documents. See page: 235
  • Weeds of California and other Western States, 2007 (ISBN 13: 978-1-879906-69-3) See Page: 525
  • Weeds of Canada, 1970 Canada Dept. of Ag., Pub. # 948, See page: 75
  • Weeds of Nebraska and the Great Plains, 1994 (ISBN 0939870-00-4) See page: 214
  • Weeds of the Northeast, 1956, Univ. of Delaware Field Manual #1 See species #: 305
  • Weeds of the Northeast, 1997 Cornell University ISBN# 0-8014-8334-4 See page: 182
  • Listed as a `Weed` by the Biota of North America Program, 2008 x
  • Listed in the WSSA Composite List of Weeds X
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