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Allium Bulbs - Ornamental Onions

Updated on September 12, 2014

Architectural Spring Bulbs

Alliums were once just onions. Now they are ornamental onions and must-have garden plants with over 700 varieties offering an irresistible range of architectural shapes and colors. Choose from giant purple drumsticks, blackberry teardrops, exquisite nodding bells and supernova-like footballs with orbiting satellites of starry flowers.

Top Ten Alliums

Here are some of the best:

1) Allium 'Ambassador'

Allium 'Ambassador' is like its parent Allium giganteum, only better; with larger spheres (up to 20cm (8") across), taller, stronger stems - 1 metre (40") - and a longer flowering season - some five weeks from late May.

This is probably the best of the newer drumstick Alliums.

Allium giganteum
Allium giganteum

2) Allium giganteum

Giant Allium

An old favourite, Allium giganteum was once the tallest Allium available, and at 150cm (5') it's still right up there. Flower heads are deep violet and large - 12.5cm across (5") - but not massive.

Allium giganteum has been awarded the RHS Award of Garden Merit.

3) Allium sphaerocephalon

Round-headed Leek

Gorgeous little burgundy teardrop flower heads and willowy stems make Allium sphaerocephalon the perfect companion for wispy windblown grasses. Other assets include pale oatmeal seed heads and a long-flowering season - up to eight weeks. Height is 60-90cm (2'-3').

4) Alliums narcissiflorum and insubricum

These two rare but sought-after Alliums are nearly identical and often confused. Both have exquisite rose purple taffeta-like bells clustered on arching stems and pointed grassy leaves during summer.

Allium Purple Sensation
Allium Purple Sensation

5) Allium hollandicum 'Purple Sensation'

Flowering Onion, Ornamental Onion

A good-value, mid-height, drumstick Allium with deep purple globes held at about 70cm (30") in May and June. At 10cm (4") across, flowers are big enough to make an impact, but not as big as giants such as Alliums Globemaster and Beau Regard.

'Purple Sensation' is a recipient of the Royal Horticultural Society's Award of Garden Merit.

Allium cristophii
Allium cristophii

6) Allium cristophii

Star of Persia

Allium cristophii's slender silver-purple star florets give its massive flower heads (20cm/8" wide) a metallic sculptural look quite unlike other Alliums. They are carried on quite short stems to about 60cm (2'), in June and July, and foliage is strappy and glaucous.

Its seed heads are spectacular in dried flower arrangements, or leave them in the garden to set seed, which will come true.

Allium cristophii is often misspelt christophii.

Allium schubertii
Allium schubertii

7) Allium schubertii

Purple Flowering Onion, Ornamental Onion

Wheels within wheels of suspended starry purple flowers, a sweet scent and enormous sparkler-like seed heads are driving Allium schubertii's popularity into the stratosphere. Plant them in hot sunny soil with Allium cristophii for a sizzling early summer display.

Allium Globemaster
Allium Globemaster

8) Allium 'Globemaster'

Giant Allium, Giant Ornamental Onion

Like many newer drumstick Allium hybrids, Globemaster has spheres that are denser, crisper and bigger - up to 20 cm (8") across - and stems that are stronger and taller - up to 90cm (3'). What's more it will repeat flower, giving you a second flush of its lovely deep purple flowers.

A very good cut flower, it will last some two weeks in a vase.

Allium Gladiator
Allium Gladiator

9) Allium 'Gladiator'

Purple Drumstick Onion

A tall, long-flowering deep lilac allium, Gladiator can make it to 150cm (5') under the right conditions - well-drained fertile soil and full sun. Flowers arrive in May and last for five weeks through to early or mid June.

It is also robust and reliable, and winner of the Royal Horticultural Society's Award of Garden Merit.

10) Allium altissimum 'Goliath'

Giant Allium, Giant Flowering Onion

Big as well as tall, Allium altissimum 'Goliath' has rotund flower heads (15cm/6") perched on 1.5m (5') stems. Actually, this is the tallest Allium currently available, with only Allium giganteum coming close.

Other plus points include a subtle scent, lilac purple flower heads and foliage that remains in place during flowering.

Alliums_Tulips
Alliums_Tulips

Early Purple Drumstick Alliums

April Alliums

Flowering in April, Allium aflatunense and Allium 'Pinball Wizard' will give you the earliest purple globes. 'Pinball Wizard' - a new and improved macleanii/cristophii hybrid will keep going until June, while it's all over for aflatunense come late May. Both are quite short though.

Try them with the April-flowering Erythronium dens-canis, which will give you contrasting lilac flowers, while April-flowering Tulips include Single Early Tulips, Greigii Tulips (early March - April), Fosteriana Tulips (mid March to April), Kaufmanniana Tulips (March to April), some Species Tulips/Botanical Tulips and Double Early Tulips (early to mid April).

Alliums for May and June

May and June bring much more choice, with Alliums 'Goliath', 'Globemaster', 'Purple Sensation' among the best. Plant them with late flowering tulips, such as Double Tulips (late), Parrot Tulips, Lily Tulips, Viridiflora Tulips, Fringed Tulips, Triumph Tulips, Darwin Tulips and Single Late Tulips for more color, while euphorbias, geraniums, Columbine, and Daylilies will bring you not only more flowers for May and June, but also lots of bushy foliage to hide the Tulips and Alliums as they go over.

For more info on which tulips flower when, see Buying Tulip Bulbs

Alliums and Daylilies

Alliums and Daylilies
Alliums and Daylilies

Allium Purple Sensation seen here with its dying foliage hidden Hemerocallis 'Marion Vaughn' and topiary hedges.

When and how to plant Allium bulbs

Generally, Allium bulbs should be planted in early autumn as follows:

  • Space tall drumstick alliums at least 20cm (8") apart. Big-headed Alliums such as cristophii and schubertii need even more space: 40cm (16") for and 30cm (12") respectively while smaller species will make do with about 10cm (4") between them.
  • Alliums can also be planted in the green. Growers begin to sell them this way in pots from about April, enabling you have Allium flowers even if you haven't had the foresight to plant the bulbs the previous autumn.

Where to plant Alliums

Alliums generally prefer sunny, fertile, well-drained soil with a PH value of about 8. The taller drumstick Alliums especially will give their best - tall strong stems and large flower heads - under these conditions, but they may need shelter from strong winds too, while Allium tuberosum, Allium nectaroscordum siculum ssp bulgaricum, Allium neapolitanum and Allium Moly, for example, will put up with more shade than most.

That said, most Alliums will tolerate a wide range of conditions, as long as they don't get waterlogged. Dig horticultural grit into the soil before planting them if necessary, rather than just adding it to the planting holes.

Allium Care
Allium Care

Allium Care

The foliage of some Alliums starts to look tatty just as they are beginning to flower. It's fine to cut it back at this point, as unlike daffodils and tulips, Alliums replenish their bulb stores from their leaves before they flower.

Alternatively hide it. Grasses, Daylilies, geraniums, hostas and Columbines will make a good job of this.

Propagating Alliums - Allium seeds, bulbils and aerial bulbils

  • Boulbous Alliums will produce bulb offsets, which should be detached and replanted in gritty compost 1 cm (.5") deep.
  • Some Alliums, such as Allium sphaerocephalon, also produce aerial bulbils, which can also be planted.
  • Many alliums will also self seed. That's fine for varieties such as Allium cristophii, which do so politely, but others, such as Allium triquetrum, and Allium moly can be extremely invasive.
  • If you want to plant your own seeds, grab the ripe brown seed heads; empty out the seed pods; and replant them straightaway or in the spring. They should germinate relatively quickly but some may take a couple years to flower.

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    • Steph Tietjen profile image

      Stephanie Tietjen 5 years ago from Albuquerque, New Mexico

      I love Alliums and have tried unsuccessfully to grow them -- I 'll have to try again with your tips. Thanks

    • Blackspaniel1 profile image

      Blackspaniel1 5 years ago

      Nice lens.

    • dahlia369 profile image

      dahlia369 5 years ago

      I never grew an allium but always admired them. Nice lens! :)

    • profile image

      AigulErali 6 years ago

      Very interesting lens!