Getting it to bloom

Why won't my Blue Boy cornflower bloom? (and how to make it flower)

Also called Blue Boy cornflower, Bachelor's button 'Blue Boy', Cornflower 'Blue Boy' (Centaurea cyanus 'Blue Boy').

More about blue boy cornflower

About Blue Boy cornflower

Centaurea cyanus 'Blue Boy' · also called Blue Boy cornflower, Bachelor's button 'Blue Boy' · flowering

'Blue Boy' is the classic intensely blue-flowered cornflower cultivar, producing large, richly coloured double blooms on tall, branching stems. An excellent cut flower and a magnet for bees and butterflies, it excels in cottage gardens and wildflower meadows. Full sun and lean, sharply drained soil produce the strongest colour and longest bloom season.

Plant type: flowering

Watch for — Faded flower colour: Blooms can become paler in very hot summers. Succession-sow every 3–4 weeks and position in a spot that receives afternoon shade in USDA zones 8–10 to extend vivid blue colour.

The reasons blue boy cornflower isn't blooming

Almost every non-blooming blue boy 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 blue boy 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 blue boy cornflower to flower

Maximise sun. Give blue boy 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 blue boy cornflower and get the feeding right with the blue boy 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

Blue Boy 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 blue boy cornflower care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Blue Boy cornflower blooming — frequently asked questions

Why won't my blue boy cornflower flower?

Blue Boy 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 blue boy cornflower bloom?

Give blue boy 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 blue boy cornflower normally bloom?