Centaurea cyanus (Cornflower)

Plant Info
Also known as: Bachelor's Buttons, Bluebottle, Garden Knapweed
Family:Asteraceae (Aster)
Life cycle:annual
Habitat:part shade, sun; disturbed soil; roadsides, fields, shores, gardens
Bloom season:June - September
Plant height:8 to 40 inches
Wetland Indicator Status:GP: FACU MW: FACU NCNE: UPL
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

Pick an image for a larger view. See the glossary for icon descriptions.

Detailed Information

Flower: Flower shape: 7+petals

[photo of flower] Showy flower heads up to about 1¼ inches across, single at the tips of branching stems. Each head has 25 to 35 florets, consisting of a series of large ray flowers around the outer edge and shorter disk flowers in the center. Ray flowers are sterile, widely spreading, funnel-shaped with 5 lobes shorter than the tube, and the color ranging from blue to purple to pink to white. Disk flowers are fertile, erect to ascending, purple to white with a column of dark blue-violet tipped stamens and a divided style.

[photo of phyllaries] The bracts (phyllaries) surrounding the base of the flower are in several layers, appressed, egg-shaped, light green with finely toothed, whitish to brown edging around the tip end, and the surface sparsely covered in matted white hairs. The entire set of phyllaries (involucre) is ½ to 2/3 inch long and longer than wide.

Leaves and stems: Leaf attachment: alternate Leaf type: simple

[photo of leaves and stem] Leaves are alternate, 1 to 4 inches long, lance-linear, pointed at the tip, stalkless, toothless or occasionally the lower leaves with a few narrow lobes. Surfaces are sparsely to moderately covered in long, matted hairs. Stems are usually single from the base, branched, sparsely to moderately covered in woolly hairs, and initially erect but tend to flop over without support of surrounding vegetation.

Fruit: Fruit type: seed_with_plume

[photo of fruit] Seeds are oblong-elliptic, 4 to 5 mm long, finely hairy, straw-colored at maturity with a tuft of short, stiff, light brown bristles at the tip.


Cornflower is an annual, native to the Mediterranean but widely naturalized far beyond its native range, and is commonly included in “wildflower” seed mixes. While not especially hardy in Minnesota, it occasionally escapes cultivation and has been noted as an agricultural pest in parts of the southeastern US. It's not likely to be confused with any other species except other garden variety Centaura species, but the woolly hairy leaves and stems should be stand-out traits. Flowers are typically blue but cultivated varieties come in a range of colors from shocking pink to purple to white.

Native Plant Nurseries, Restoration and Landscaping Services ↓

Map of native plant resources in the upper midwest

  • Shop for native seeds and plants at PrairieMoon.com!
  • Shooting Star Native Seeds - Native Prairie Grass and Wildflower Seeds
  • Morning Sky Greenery - Native Prairie Plants
  • Natural Shore Technologies - Using science to improve land and water
  • Minnesota Native Landscapes - Your Ecological Problem Solvers

More photos

Photos by K. Chayka and Peter M. Dziuk taken in the garden. C. cyanus at the edge of a field by Stefan.lefnaer, via Wikimedia Commons, used under CC BY-SA 4.0


Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: bruce honnigford - Minnetonka
on: 2021-05-26 19:59:07

I have one growing on a sunny hillside end of May.

Posted by: Suzie - Bloomington
on: 2021-06-12 06:40:46

Several of them sprang up in my front garden this year.

Posted by: Kelsey - Hennepin County
on: 2021-06-14 08:07:08

Growing up next to our house (we just moved in). Doesn't look planted as it is a single specimen. I do have corn flower in my garden, but that is a completely different size and color so it definitely didn't escape my garden.

Post a comment

Note: All comments are moderated before posting to keep the spammers out. An email address is required, but will not be posted—it will only be used for information exchange between the 2 of us (if needed) and will never be given to a 3rd party without your express permission.

For info on subjects other than plant identification (gardening, invasive species control, edible plants, etc.), please check the links and invasive species pages for additional resources.


Note: Comments or information about plants outside of Minnesota and neighboring states may not be posted because Id like to keep the focus of this web site centered on Minnesota. Thanks for your understanding.