Cornflower, Garden Cornflower
General: Annual flowering plant in the daisy family (Asteraceae).
Flowers: Are pompom-like, with bracts at the base and fringed margins. They are typically greater than 3 cm wide. The marginal flowers are bell-shaped with enlarged irregular corollas. Flowers are typically blue, but can also be purple, pink, or white.
Stem: Mature plants are 0.2 – 1.2 m tall. Stems are greyish-green, branched, erect, and loosely hairy.
Leaves: Are grey-green, matte, and lanceolate with narrow upper leaves and smooth edges. The lower leaves can be toothed or lobed along the margins. They can be up to 13 cm long and 1 cm wide.
Fruit: Are 4 – 5 mm long with fine, hairy bristles attached to one end. The seeds are typically straw-coloured.
Habitat and Origin
Bachelor’s Button is native to Southern Europe where it is known as ‘cornflower’ and is commonly found in grain fields. It is now considered endangered in its native habitat.
Bachelor’s Button prefers dry disturbed areas such as roadsides, riverbanks, meadows, fields, and grasslands.
Propagation & Vectors of Spread
Bachelor’s Button reproduces through seeds. They germinate very quickly after planting, which helps the plant spread quickly.
Bachelor’s Button is spread by gardeners; it is often planted in gardens and is commonly found in wildflower seed mixes. Bachelor’s Button is also often found as a contaminant in crop seed. Moreover, seeds are spread by wind, water, and birds that eat the seeds.
Ecological & Economic Impacts
- Outcompetes native vegetation in meadows and grassland habitats.
- Decreases moisture and nutrients available in the soil.
- Reduces crop yields due to dense colonies.
- Crowds out forage yields.
What Can I Do?
Bachelor’s Button is currently found throughout the Sea to Sky Corridor, so the best approach to controlling its spread is by PREVENTION.
Learn to identify Bachelor’s Button: use the images presented in this profile page to learn how to identify Bachelor’s Button.
What to do if you spot it: You can report any Bachelor’s Button sighting by clicking here.
- Regularly monitor properties for weed infestations.
- Ensure soil and gravel are uncontaminated before transport.
- Check wildflower mixes to ensure that they do not contain Bachelor’s Button.
- Ensure that plants are disposed of in a garbage bag if found in floral arrangements to prevent seeds from spreading.
- Do not 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.
- Do not plant Bachelor’s Button in a garden, no matter how well-contained its enclosure may seem.
- Do not move soil that has been contaminated with Bachelor’s Button.
- Do not compost
- Repeated hand-pulling, removing the entire root system is the most effective way to reduce Bachelor’s Button.
- Regular mowing/tilling can reduce weed progression; material can be left on-site to decompose if the plant has not started flowering yet.
- Once Bachelors’ Button has flowered, all plant parts must be bagged and deeply buried at the landfill.
- When tilling, be sure to prevent machinery from spreading root fragments to new sites by washing it.
- Plants should be treated when they are in the rosette stage.
- Control of Bachelor’s Button has been documented using a mixture of glyphosate and aminopyralid or glyphosate and clopyralid at the chemical label’s recommended rate.
- 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 control agents currently available for this plant.
- Electronic Atlas of the Flora of BC, Cornflower, http://linnet.geog.ubc.ca/Atlas/Atlas.aspx?sciname=Centaurea%20cyanus
- Invasive Species Council of BC, Bachelor’s Button, https://bcinvasives.ca/invasives/bachelors-button/
- Invasive Plant Atlas of the United States, Cornflower, https://www.invasiveplantatlas.org/subject.html?sub=5269
- Missouri Botanical Garden, Cornflower, http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=277177
- PlantWise, Bachelor’s Button, http://beplantwise.ca/invasives/detail/1676
- Tennessee Invasive Plant Council, Bachelor’s Button, https://www.tnipc.org/invasive-plants/plant-details/?id=105
- Washington State Noxious Weed Control Board, Bachelor’s Button, https://www.nwcb.wa.gov/weeds/bachelors-button
- Wikipedia, Centaurea cyanus, https://en.wikipedia.org/wiki/Centaurea_cyanus