Getting it to bloom

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

Also called Purple Sensation allium, ornamental onion, purple globe allium (Allium hollandicum 'Purple Sensation').

More about allium 'purple sensation'

About Allium 'Purple Sensation'

Allium hollandicum 'Purple Sensation' · also called Purple Sensation allium, ornamental onion · flowering

Allium hollandicum 'Purple Sensation' is a popular ornamental onion bearing dense, rounded umbels of star-shaped deep-violet flowers on tall bare stems in late spring to early summer. The strappy basal leaves fade as it blooms. Easy, drought-tolerant and bee-friendly, it naturalises in sunny borders. All parts are toxic to cats and dogs.

Plant type: flowering

Watch for — Tatty foliage at bloom time: The strappy leaves yellow and flop just as the flowers open, which looks untidy. Plant among perennials or grasses that hide the fading foliage.

The reasons allium 'purple sensation' isn't blooming

Almost every non-blooming allium 'purple sensation' 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 'purple sensation' 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 'purple sensation' to flower

Maximise sun. Give allium 'purple sensation' 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 'purple sensation' and get the feeding right with the allium 'purple sensation' 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 'Purple Sensation' 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 'purple sensation' care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Allium 'Purple Sensation' blooming — frequently asked questions

Why won't my allium 'purple sensation' flower?

Allium 'Purple Sensation' 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 'purple sensation' bloom?

Give allium 'purple sensation' 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 'purple sensation' normally bloom?