Weed Information: Oenothera elata (eveningprimrose, Hooker's)
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Oenothera elata (eveningprimrose, Hooker's)

Family: Onagraceae

Description

This species is very similar to Oenothera strigosa and Oenothera erythrosepala but can be distinguished by its larger petals (2.5 to 4 cm long) and its more narrow leaves which are usually less than 1/4 as wide as long. Also extremely similar to Oenothera villosa but sparsely rather than densely hairy.

Characteristics

Flower Color
  • Red-orange
  • Yellow
Inflorescence Type (How the flowers are arranged on the plant)
  • Solitary, axillary
  • Terminal spike
Number of Petals
  • 4 petals
Petal Separation
  • Completely free to base
  • United from 25% - 75% length
Petal Tip
  • Rounded
  • Square
Flower Symmetry
  • Flowers regular
Flower Length (Head length in the Asteraceae)
  • 2.5 cm (1.0 inch)
  • 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) or more
Flower Width (Head width in the Asteraceae)
  • 5.0 cm (2.0 inches)
  • > 5.0 cm (> 2.0 inches)
Number of Sepals
  • 4 sepals
Sepal Separation
  • Completely free to base
  • United from 25% - 75% length
Sepal Tip
  • Pointed
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
  • 2.5 cm (1.0 inch)
  • 3.0 cm (1.2 inches)
  • 3.5 cm (1.4 inches)
  • 4.0 cm (1.6 inches)
  • 4.5 cm (1.8 inches)
Fruit Width at Maturity
  • 4 mm (.16 inch)
  • 5 mm (.20 inch)
  • 6 mm (.24 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 25% - 75% total length
Leaf Length (blade PLUS petiole)
  • 4 - 10 cm (1.60 - 4.0 inches)
  • 1 - 2 dm (4.0 - 8.0 inches)
  • 2 - 4 dm (8.0 - 16.0 inches)
Leaf Width
  • 1 - 2 cm (.40 - .80 inch)
  • 2 - 4 cm (.80 - 1.6 inches)
Leaf Shape (simple leaves only)
  • Elliptic
  • Lanceolate
  • Oblanceolate
Leaf or Leaflet Margin
  • Dentate
  • Undulate (sinuate, repand)
Leaf or Leaflet Blade Base
  • Acute (cuneate)
  • Acuminate (attenuate)
Leaf or Leaflet Tip
  • Acute
  • Rounded (obtuse)
Leaf or Leaflet Blade Surface
  • Glandular
  • Hirsute
  • Pubescent
  • Sericeous or villous (silky)
  • Strigose
  • Villous or sericious (silky)
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
  • Biennial
  • Perennial
Growth Habit (while flowering)
  • Erect, columnar (narrow)
Plant Height at Maturity
  • 4 - 6 dm (1.3 - 2.0 feet)
  • 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
  • Mesic
  • Arid
Chlorophyll
  • Present

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

Root or Vegetative Propagule
  • Tap Root

US State
  • Kansas
  • Texas
  • Arizona
  • California
  • Colorado
  • Idaho
  • Montana
  • New Mexico
  • Nevada
  • Oklahoma
  • Oregon
  • Utah
  • Washington
  • Wyoming
Canadian Province or Territory
  • Manitoba

  • California Growers Weed Identification Handbook, 1968 - 1998 University of California Publication # 4030-1, See page: 155
  • Weeds of California and other Western States, 2007 (ISBN 13: 978-1-879906-69-3) See Page: 971
  • Listed as a `Weed` by the Biota of North America Program, 2008 x
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