Oenothera biennis L.
Evening star, Sundrop, King’s cure-all, Weedy evening primrose
General: Common Evening-Primrose is a biennial in the Onagraceae family.
Flowers: Clusters of yellow flowers form at the tips of branches. The florets contain four heart-shaped petals and emit a light lemon scent. Notably, flowers bloom from the bottom up and typically remain open from evening to early morning.
Stem: Are upright (up to 1.8 m tall), green and woody. Common Evening-Primrose typically has a central stem but may branch out when growing in open areas, creating a bushy appearance. The lower half of the stem may have a purple tinge.
Leaves: Are alternate, lanceolate, light or olive green, and have edges that are smooth and nearly hairless. Smaller secondary leaves may develop between the leaf stalk and the central stem.
Fruit: Are encased in long, narrow seedpods that taper toward the end. When dry, seed pods split downward to release numerous tiny, irregular seeds.
Roots: Thick, fleshy, and deep taproot.
Sulphur Cinquefoil (Potentilla recta) flowers are paler than Common Evening-Primrose’s and have five petals. Leaves are distinctly toothed and arranged in a palm-like formation.
Northern Evening Primrose (Oenothera parviflora) has smaller flowers and a small ridge on the end of the sepal. Northern Evening Primrose also tends to be covered in more hairs than Common Evening-Primrose.
Habitat and Origin
This species is native to eastern and central North America.
Common Evening-Primrose is a versatile plant, capable of growing in various light and soil conditions. It is found in a variety of habitats, including rocky plains, lakeshores, open woods and disturbed areas such as vacant lots, roadsides, railroads, and abandoned fields. Common Evening-Primrose is often cultivated in wildflower gardens as well.
Propagation & Vectors of Spread
Common Evening-Primrose spreads by seed, which can remain in soil for over 70 years. It is common to find 100 capsules on a plant and over 100 seeds in each capsule.
The tiny seeds are easily dispersed by wind and birds. Common Evening-Primrose is also sometimes included in wildflower gardens and seed mixes, which aids its spread.
Ecological, Economic, & Health Impacts
- Reduces biodiversity.
- Spreads rapidly, displacing native vegetation.
- Unsuitable for forage (not poisonous, but its texture is unpalatable to animals).
- Reduces hay quality.
What Can I Do?
Common Evening-Primrose is found in the Sea to Sky region and its distribution is beyond landscape-level control. When Common Evening-Primrose is present at high-priority locations and negatively impacting them, their control is considered a high priority.
Otherwise, the goal is to prevent it from spreading to new (uninfested) areas, and to control it where possible to limit its impact on biodiversity.
Learn to identify Common Evening-Primrose: use the images presented on this page to learn how to identify Common Evening-Primrose
What to do if you spot it: You can report any Common Evening-Primrose sighting by clicking here.
- Minimize soil disturbances (e.g. use grazing plans that prevent soil exposure from overgrazing), and use seed mixes with dense, early colonization (e.g. alfalfa or barley) to re-vegetate exposed soil and resist invasion.
- Ensure plants (particularly flowering heads or root fragments) are bagged or covered to prevent spread during transport to designated disposal sites (e.g. landfill).
- Regularly monitor properties for weed infestations.
- Ensure soil and gravel are uncontaminated before transport.
- Check wildflower seed mixes to see if they contain Common Evening-Primrose
- Unload, park or store equipment or vehicles in infested areas; remove plant material from any equipment, vehicles or clothing used in such areas and wash equipment and vehicles at designated cleaning sites before leaving infested areas.
- Plant Common Evening-Primrose in a garden, no matter how well-contained its enclosure may seem.
- Move soil that has been contaminated with Common Evening-Primrose.
Digging out rosettes, mowing or hoeing while the plant is in the rosette stage may help control an infestation, but the seeds spread easily, making mechanical control alone difficult.
If applied in early spring, 2,4-D or dicamba combined with glyphosate have proven effective at controlling infestations.
We recommend that any herbicide application is carried out by a person holding a valid BC Pesticide Applicator Certificate. Before selecting and applying herbicides, you must review and follow herbicide labels and application rates; municipal, regional, provincial and federal laws and regulations; species-specific treatment recommendations, and site-specific goals and objectives.
There are no biological controls available for this plant.
You can hinder Common Evening-Primrose’s growth and spread by encouraging native grass competition.
- BC Ministry of Forests, Lands and Natural Resources Operations, Pale Evening-primrose (Oenothera pallida ssp. pallida), https://www2.gov.bc.ca/assets/gov/environment/natural-resource-stewardship/best-management-practices/okanagan/oenothera_pallida_ssp_pallida.pdf
- Electronic Atlas of the Flora of British Columbia, Oenothera biennis L., http://linnet.geog.ubc.ca/Atlas/Atlas.aspx?sciname=Oenothera%20biennis
- Invasive Species Compendium, Oenothera biennis (common evening primrose), https://www.cabi.org/isc/datasheet/115863
- Minnesota Wildflowers, Oenothera biennis (Common Evening Primrose), https://www.minnesotawildflowers.info/flower/common-evening-primrose
- Mississippi State University Extension, Weed of the Week: Cutleaf Evening-primrose, https://www.mississippi-crops.com/2012/10/17/weed-of-the-week-cutleaf-evening-primrose/
- Ontario Weed Committee, Yellow evening primrose, Oenothera biennis, https://www.weedinfo.ca/en/weed-index/view/id/OEOBI
- USDA Natural Resources Conservation Service, Oenothera biennis L., https://plants.usda.gov/home/plantProfile?symbol=OEBI