Getting it to bloom

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

Also called sky blue aster, azure aster (Symphyotrichum oolentangiense).

More about sky blue aster

About Sky Blue Aster

Symphyotrichum oolentangiense · also called sky blue aster, azure aster · flowering

Sky blue aster is a slender, drought-tough native perennial bearing airy sprays of small azure-blue daisies with yellow centres in autumn. Adapted to dry prairies and rocky open ground, it thrives in full sun and lean, well-drained soil. Its distinctive heart-shaped basal leaves feel sandpapery, and its late blooms feed bees and butterflies before winter.

Plant type: flowering

Watch for — Sparse bloom in shade: Too little sun yields lanky stems and few flowers. Relocate to a fully sunny, open position to restore its characteristic cloud of azure daisies.

The reasons sky blue aster isn't blooming

Almost every non-blooming sky blue 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 sky blue 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 sky blue aster to flower

Maximise sun. Give sky blue 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 sky blue aster and get the feeding right with the sky blue 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

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

Sky Blue Aster blooming — frequently asked questions

Why won't my sky blue aster flower?

Sky Blue 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 sky blue aster bloom?

Give sky blue 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 sky blue aster normally bloom?