Photo by Melody

PlantFiles: Bachelor's Button, Cornflower
Centaurea cyanus 'Blue Diadem'

Family: Asteraceae (ass-ter-AY-see-ee) (Info)
Genus: Centaurea (sen-TAR-ee-uh) (Info)
Species: cyanus (SY-an-us) (Info)
Cultivar: Blue Diadem

One vendor has this plant for sale.

3 members have or want this plant for trade.


24-36 in. (60-90 cm)

6-9 in. (15-22 cm)

Not Applicable

Sun Exposure:
Full Sun


Bloom Color:
Medium Blue

Bloom Time:
Late Spring/Early Summer
Mid Summer
Late Summer/Early Fall


Other details:
This plant is attractive to bees, butterflies and/or birds
Average Water Needs; Water regularly; do not overwater
Self-sows freely; deadhead if you do not want volunteer seedlings next season
Flowers are good for drying and preserving

Soil pH requirements:
7.6 to 7.8 (mildly alkaline)
7.9 to 8.5 (alkaline)

Patent Information:
Unknown - Tell us

Propagation Methods:
From seed; direct sow outdoors in fall
From seed; winter sow in vented containers, coldframe or unheated greenhouse
From seed; sow indoors before last frost
From seed; direct sow after last frost

Seed Collecting:
Collect seedhead/pod when flowers fade; allow to dry
Allow seedheads to dry on plants; remove and collect seeds
Properly cleaned, seed can be successfully stored

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to view:

By LilyLover_UT
Thumbnail #1 of Centaurea cyanus by LilyLover_UT

By rebecca101
Thumbnail #2 of Centaurea cyanus by rebecca101

By Calif_Sue
Thumbnail #3 of Centaurea cyanus by Calif_Sue

By Calif_Sue
Thumbnail #4 of Centaurea cyanus by Calif_Sue

By Calif_Sue
Thumbnail #5 of Centaurea cyanus by Calif_Sue

By AnniesAnnuals
Thumbnail #6 of Centaurea cyanus by AnniesAnnuals

By AnniesAnnuals
Thumbnail #7 of Centaurea cyanus by AnniesAnnuals


2 positives
No neutrals
No negatives

Gardeners' Notes:

Positive rebecca101 On Sep 26, 2007, rebecca101 from Madison, WI (Zone 5a) wrote:

This was a very fine bachelor's button, although overall I'd say not worth the extra $$ I shelled out for it as compared to the cheap standard varieties. The flowers on Blue Diadem are a bit more refined looking - they're flatter and somewhat larger. A lovely shade of blue. I didn't find them to be as large as advertised though (the source I bought them from claimed they get to be 4" across - mine were nowhere near that.)

Positive LilyLover_UT On Jan 16, 2005, LilyLover_UT from Ogden, UT (Zone 5b) wrote:

This tall cornflower has striking, bright blue, double flowers and silvery-green foliage. 'Blue Diadem' has larger flowers than most varieties. Cornflowers attract a wide range of beneficial insects.


This plant has been said to grow in the following regions:

Redwood City, California
Richmond, California
San Jose, California
Charleston, West Virginia
Madison, Wisconsin

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