Weed Information: Epilobium ciliatum (willowweed, American)
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Epilobium ciliatum (willowweed, American)

Family: Onagraceae

Description

Also called northern willow herb. Common in wet areas. The young leaves are deep purple on the back. All leaves with minute, widely spaced teeth on the margin.

Characteristics

Flower Color
  • Red (or pink)
  • Blue-purple
  • Purple
  • Red-purple
  • White
Inflorescence Type (How the flowers are arranged on the plant)
  • Solitary, axillary
  • Terminal raceme
Number of Petals
  • 4 petals
Petal Separation
  • Completely free to base
Petal Tip
  • Bilobed
Flower Symmetry
  • Flowers regular
Flower Length (Head length in the Asteraceae)
  • 2 mm (.08 inch)
  • 3 mm (.12 inch)
  • 4 mm (.16 inch)
Flower Width (Head width in the Asteraceae)
  • 6 mm (.24 inch)
  • 7 mm (.28 inch)
  • 8 mm (.32 inch)
Number of Sepals
  • 4 sepals
Sepal Separation
  • Completely free to base
Sepal Tip
  • Pointed
  • Rounded
Flower Sex
  • Bisexual (perfect)
Number of Styles
  • 1 style
Number of Stamens
  • 8 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
  • 4 carpels
Ovary Position
  • Inferior (epigynous)
Fruit Type
  • Capsule, > 3-celled
Fruit Length at Maturity
  • 3.0 cm (1.2 inches)
  • 3.5 cm (1.4 inches)
  • 4.0 cm (1.6 inches)
  • 4.5 cm (1.8 inches)
  • 5.0 cm (2.0 inches)
  • 6.0 cm (2.4 inches)
  • 7.0 cm (2.8 inches)
  • 8.0 cm (3.2 inches)
Fruit Width at Maturity
  • 1 mm (.04 inch) or less
  • 2 mm (.08 inch)
  • 3 mm (.12 inch)
Burs
  • Fruit or seed NOT bur-like

Leaf Arrangement
  • Alternate
  • Alternate below, opposite above
  • Opposite
  • Opposite below, alternate above
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)
  • 2 - 4 cm (.80 - 1.60 inches)
  • 4 - 10 cm (1.60 - 4.0 inches)
Leaf Width
  • 5 - 10 mm (.20 - .40 inch)
  • 1 - 2 cm (.40 - .80 inch)
Leaf Shape (simple leaves only)
  • Elliptic
  • Lanceolate
Leaf or Leaflet Margin
  • Dentate
  • Entire
Leaf or Leaflet Blade Base
  • Acute (cuneate)
  • Rounded
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
  • Perennial
Growth Habit (while flowering)
  • 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)
  • 8 - 10 dm (2.6 - 3.3 feet)
Wind Dissemination
  • Fruit, seed, or spore wind borne
Moisture Regime
  • Semi-aquatic
  • Seasonally saturated
  • Mesic
Chlorophyll
  • Present

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

Root or Vegetative Propagule
  • Fibrous
  • Rhizomatous
  • Tap Root

US State
  • Connecticut
  • Delaware
  • Illinois
  • Kansas
  • Kentucky
  • Massachusetts
  • Maine
  • Michigan
  • North Carolina
  • New Hampshire
  • New Jersey
  • New York
  • Ohio
  • Pennsylvania
  • South Carolina
  • Tennessee
  • Texas
  • Virginia
  • Wisconsin
  • West Virginia
  • Hawaii
  • 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
  • Northwest Territory
Other
  • District of Columbia
  • St. Pierre and Miquelon
  • Labrador

  • California Growers Weed Identification Handbook, 1968 - 1998 University of California Publication # 4030-1, See page: 186
  • Common Weeds of the Canadian Prairies, 1963 (Cat# A53-1136-1) See page: 36
  • Northwest Weeds, 1990 (ISBN 0-87842-249-8) See page: 91
  • Weeds of California and other Western States, 2007 (ISBN 13: 978-1-879906-69-3) See Page: 955
  • Weeds of the Northeast, 1997 Cornell University ISBN# 0-8014-8334-4 See page: 254
  • 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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