Weed Information: Iris pseudacorus (iris, yellowflag)
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Iris pseudacorus (iris, yellowflag)

Family: Iridaceae

Description

A beautiful escaped ornamental, this species is always found in, or along the margins of, water bodies. At maturity the seed pods droop over the water and open, releasing their large seeds which then float away to cause further infestations. The rhizomes form solid mats, excluding all other vegetation and inhibiting the flow of streams and irrigation canals.

Characteristics

Flower Color
  • Yellow
  • Brown/Black
  • Multi-colored
Inflorescence Type (How the flowers are arranged on the plant)
  • Solitary, terminal
  • Terminal raceme
Number of Petals
  • 3 petals
  • 6 petals
Petal Separation
  • Completely free to base
Petal Tip
  • Pointed
  • Rounded
Flower Symmetry
  • Flowers regular
Flower Length (Head length in the Asteraceae)
  • 5.0 cm (2.0 inches) or more
Flower Width (Head width in the Asteraceae)
  • > 5.0 cm (> 2.0 inches)
Number of Sepals
  • sepals lacking
  • 3 sepals
Sepal Separation
  • Completely free to base
Sepal Tip
  • Rounded
Flower Sex
  • Bisexual (perfect)
Number of Styles
  • 1 style
Number of Stamens
  • 3 stamens
Stamens Attached to the Petals
  • Stamens NOT attached to the petals
Stamens Connate (united)
  • Filaments united, monodelphous

Carpel Separation
  • Carpels united (or one)
Number of Carpels
  • 3 carpels
Ovary Position
  • Inferior (epigynous)
Fruit Type
  • Capsule, 3-celled
Fruit Length at Maturity
  • 7.0 cm (2.8 inches)
  • 8.0 cm (3.2 inches)
  • 9.0 cm (3.6 inches)
  • 1.0 dm (4.0 inches)
Fruit Width at Maturity
  • 1.5 cm (.60 inch)
  • 2.0 cm (.80 inch)
  • 2.5 cm (1.0 inch)
Burs
  • Fruit or seed NOT bur-like

Leaf Arrangement
  • Alternate
Leaf Type
  • Simple (including lobed leaves)
Stipules
  • Lacking
Tendrils
  • Tendrils absent
Venation
  • Parallel
Petiole (leaf stem) Blade Ratio
  • Petiole absent (leaf sessile)
Leaf Length (blade PLUS petiole)
  • 4 - 6 dm (1.3 - 2.0 feet)
  • > 6 dm (> 2.0 feet)
Leaf Width
  • 1 - 2 cm (.40 - .80 inch)
  • 2 - 4 cm (.80 - 1.6 inches)
Leaf Shape (simple leaves only)
  • Linear or filiform
Leaf or Leaflet Margin
  • Entire
Leaf or Leaflet Blade Base
  • Clasping
Leaf or Leaflet Tip
  • Acuminate (attenuate)
  • Acute
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
  • Perennial
Growth Habit (while flowering)
  • Erect, columnar (narrow)
Plant Height at Maturity
  • 6 - 8 dm (2.0 - 2.6 feet)
  • 8 - 10 dm (2.6 - 3.3 feet)
  • 1 - 1.5 meters (3.3 - 5.0 feet)
Wind Dissemination
  • Not wind disseminated
Moisture Regime
  • Aquatic
  • Semi-aquatic
Chlorophyll
  • Present

Stem Cross Section
  • Round
Flowering Stem Leaves
  • Stem leafless
  • Stem leaves greatly reduced
  • Stem uniformly leafy
Main Stem Branches
  • Main stem unbranched
  • Main stem branched

Root or Vegetative Propagule
  • Bulb or Corm
  • Rhizomatous

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
  • California
  • Iowa
  • Idaho
  • Minnesota
  • Montana
  • New Mexico
  • Nevada
  • Oregon
  • Utah
  • Washington
  • Nebraska
Canadian Province or Territory
  • British Columbia
  • New Brunswick
  • Nova Scotia
  • Ontario
  • Prince Edward Island
  • Quebec
  • Manitoba
  • Newfoundland
Other
  • District of Columbia
  • Labrador

  • Aquatic and Riparian Plants of the West, 2003 (ISBN# 1-879906-59-7) See page: 221
  • Weeds of California and other Western States, 2007 (ISBN 13: 978-1-879906-69-3) See Page: 859
  • 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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