Getting it to bloom

Why won't my Allium schubertii bloom? (and how to make it flower)

Also called tumbleweed onion, Schubert allium, starburst allium (Allium schubertii).

More about allium schubertii

About Allium schubertii

Allium schubertii · also called tumbleweed onion, Schubert allium · flowering

Allium schubertii is a striking ornamental onion whose huge, loose umbel resembles an exploding firework — pinkish-purple flowers held on unequal-length stalks creating a starburst up to 30 cm across in early summer. The dried seedhead tumbles like tumbleweed and is prized for arrangements. It needs full sun, sharp drainage and a hot, dry summer, and is toxic to cats and dogs.

Plant type: flowering

Watch for — Bulb rot from summer wet: More than most alliums, it rots in damp or poorly drained soil during its dormant summer rest. Grow in very gritty soil or pots and keep bone-dry after flowering.

The reasons allium schubertii isn't blooming

Almost every non-blooming allium schubertii 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 allium schubertii 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 allium schubertii to flower

Maximise sun. Give allium schubertii 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 allium schubertii and get the feeding right with the allium schubertii 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

Allium schubertii 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 allium schubertii care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Allium schubertii blooming — frequently asked questions

Why won't my allium schubertii flower?

Allium schubertii 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 allium schubertii bloom?

Give allium schubertii 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 allium schubertii normally bloom?