Getting it to bloom

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

Also called China aster, Annual aster, Garden aster (Callistephus chinensis).

More about china aster

About China aster

Callistephus chinensis · also called China aster, Annual aster · flowering

China aster is a half-hardy annual producing abundant daisy-like flowers in white, pink, red, blue, and purple from mid-summer to autumn. It excels as a cut flower and bedding plant. Grow in full sun in fertile, well-drained soil. Susceptible to aster wilt; crop rotation and good hygiene are essential for healthy plants.

Plant type: flowering

Watch for — Aster yellows (phytoplasma): Transmitted by leafhoppers; symptoms include yellowing foliage, stunted growth, virescent (green-tinged) flowers, and witches' broom distortion. There is no cure — remove and destroy infected plants. Control leafhoppers with insect-proof mesh over seedlings and keep the surrounding area weed-free.

The reasons china aster isn't blooming

Almost every non-blooming china aster 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 china aster 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 china aster to flower

Maximise sun. Give china aster 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 china aster and get the feeding right with the china aster 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

China aster 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 china aster care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

China aster blooming — frequently asked questions

Why won't my china aster flower?

China aster 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 china aster bloom?

Give china aster 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 china aster normally bloom?