Getting it to bloom

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

Also called New York aster, Michaelmas daisy, Novi-belgii aster (Symphyotrichum novi-belgii).

More about new york aster

About New York aster

Symphyotrichum novi-belgii · also called New York aster, Michaelmas daisy · flowering

New York aster is the classic Michaelmas daisy of British and North American autumn gardens, producing masses of blue, violet, pink, or white daisy flowers from late August to October. It forms vigorous clumps, spreads readily by rhizome, and supports late-season pollinators. Heights range from compact 30 cm dwarfs to tall 120 cm border plants depending on cultivar.

Plant type: flowering

Watch for — Overcrowding and blind shoots: Clumps spread aggressively and become crowded within 2 years, producing many non-flowering blind shoots. Divide every 2 years in spring, replanting small divisions from the clump margins.

The reasons new york aster isn't blooming

Almost every non-blooming new york 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 new york 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 new york aster to flower

Maximise sun. Give new york 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 new york aster and get the feeding right with the new york 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

New York 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 new york aster care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

New York aster blooming — frequently asked questions

Why won't my new york aster flower?

New York 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 new york aster bloom?

Give new york 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 new york aster normally bloom?