Getting it to bloom

Why won't my Thunberg's astilbe bloom? (and how to make it flower)

Also called Thunberg's astilbe, Japanese astilbe (Astilbe thunbergii).

More about thunberg's astilbe

About Thunberg's astilbe

Astilbe thunbergii · also called Thunberg's astilbe, Japanese astilbe · flowering

A vigorous, late-blooming herbaceous perennial from Japan with elegant, drooping flower plumes in white or pale pink, rising above finely divided, dark-green foliage. It naturalises readily in moist, shaded woodland or waterside settings and is fully frost hardy. Non-toxic to pets. Young leaves are historically used to make tea in Japan.

Plant type: flowering

Watch for — Declining vigour: Older clumps become congested and flower less freely after 4–5 years. Lift and divide in spring to reinvigorate, discarding the woody central section and replanting outer portions.

The reasons thunberg's astilbe isn't blooming

Almost every non-blooming thunberg's astilbe 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 thunberg's astilbe 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 thunberg's astilbe to flower

Maximise sun. Give thunberg's astilbe 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 thunberg's astilbe and get the feeding right with the thunberg's astilbe 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

Thunberg's astilbe 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 thunberg's astilbe care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Thunberg's astilbe blooming — frequently asked questions

Why won't my thunberg's astilbe flower?

Thunberg's astilbe 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 thunberg's astilbe bloom?

Give thunberg's astilbe 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 thunberg's astilbe normally bloom?