Getting it to bloom

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

Also called Alpine Aster, Rock Aster (Aster alpinus).

More about alpine aster

About Alpine Aster

Aster alpinus · also called Alpine Aster, Rock Aster · flowering

Alpine Aster is a neat, clump-forming perennial from subalpine meadows and rocky slopes across Europe and western North America. In late spring and early summer it produces classic daisy-like flowers with violet-purple rays around a yellow centre, borne singly on short stems. A reliable, easy alpine for rock gardens, raised beds, and sunny borders.

Plant type: flowering

Watch for — Decline after several years: Clumps become woody and flower less prolifically after 3–4 years. Divide in early spring every 2–3 years, replanting vigorous outer sections and discarding the exhausted woody centre.

The reasons alpine aster isn't blooming

Almost every non-blooming alpine 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 alpine 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 alpine aster to flower

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

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

Alpine Aster blooming — frequently asked questions

Why won't my alpine aster flower?

Alpine 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 alpine aster bloom?

Give alpine 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 alpine aster normally bloom?