Getting it to bloom

Why won't my Cornflower bloom? (and how to make it flower)

Also called Cornflower, Bachelor's Button, Bluebottle, Ragged Sailor (Centaurea cyanus).

More about cornflower

About Cornflower

Centaurea cyanus · also called Cornflower, Bachelor's Button · flowering

Centaurea cyanus is a slender, fast-growing annual originally native to grain fields across Europe and now widely cultivated worldwide for its vivid, true-blue flowers, which appear from May through September with successive sowings. It thrives in poor to moderately fertile, well-drained soil in full sun, and is one of the easiest annuals for cut flower or wildflower meadow use — sowing directly where it is to flower gives the best results as it dislikes root disturbance. Deadhead regularly to extend the prolific flowering season. The ASPCA lists cornflower (Centaurea cyanus) as non-toxic to cats and dogs.

Plant type: flowering

Watch for — Aphids: Black bean aphid (Aphis fabae) and other species cluster on stem tips and buds in early summer; blast off with water or apply an insecticidal soap spray, as heavy infestations distort and abort flowers.

The reasons cornflower isn't blooming

Almost every non-blooming cornflower traces back to one of these, roughly in order of how common they are:

Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.
Too much nitrogen feed, driving lush foliage at the expense of flowers (very common with general or lawn feeds).
The plant has not been deadheaded, so it stops flowering once it sets seed.
Irregular watering — drought or waterlogging at the budding stage makes buds abort.
It is still too young or was checked by a transplant and is rebuilding before flowering.

Feeding cornflower a high-nitrogen general feed and growing it in too little sun — you get a big leafy plant and almost no flowers.

The fix — how to get cornflower to flower

Maximise sun. Give cornflower the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers.
Switch the feed. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.
Deadhead regularly. Remove spent flowers often to keep it producing more rather than stopping to set seed.
Water consistently. Keep moisture even through budding and flowering — drought-then-flood swings make buds drop.

Light and feeding do most of the heavy lifting here. Dial in the spot with the light guide for cornflower and get the feeding right with the cornflower fertilising schedule — the wrong feed (too much nitrogen) is one of the most common silent reasons a healthy plant makes leaves instead of flowers.

Bloom season and what to expect

Cornflower flowers across its growing season (mostly summer) and, kept fed and deadheaded, can bloom for many weeks or right up to frost.

Post-bloom care so it flowers again

Deadhead, keep feeding lightly, and many will rebloom; collect seed from the best plants at the end of the season if you want to grow them again.

For everything else this plant needs day to day, see the full cornflower care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Cornflower blooming — frequently asked questions

Why won't my cornflower flower?

Cornflower blooms on the season's growth given enough sun, warmth and the right feed — there is no cold or photoperiod trick, just good growing conditions and a bloom-leaning feed. The most common reason it is not happening: Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.

How do I make cornflower bloom?

Give cornflower the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.

When does cornflower normally bloom?