Getting it to bloom

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

Also called smooth blue aster, smooth aster (Symphyotrichum laeve).

More about smooth blue aster

About Smooth Blue Aster

Symphyotrichum laeve · also called smooth blue aster, smooth aster · flowering

Smooth blue aster is an elegant native perennial with smooth, blue-green foliage and clouds of soft blue-violet daisy flowers in autumn. More drought- and mildew-tolerant than New England aster, it favours full sun and well-drained soil. Its sturdy, upright stems rarely need staking, and its late blooms are a key food source for pollinators.

Plant type: flowering

Watch for — Aphids on new growth: Soft new shoots and buds can attract aphids. Hose them off or tolerate them, as beneficial insects usually keep colonies in check on a healthy plant.

The reasons smooth blue aster isn't blooming

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

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

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

Smooth Blue Aster blooming — frequently asked questions

Why won't my smooth blue aster flower?

Smooth 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 smooth blue aster bloom?

Give smooth 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 smooth blue aster normally bloom?