How to Grow Allium

closeup of pink alliumcloseup of pink allium

If you want to look like you’ve taken your garden to the next level of design, ornamental alliums are the answer. Planting a few bulbs in the fall will create a mini-sculpture garden in the spring that will not only last while the flowers are fresh, but continue into summer as the flowers dry in place. The single globes float above the surrounding garden and are made up of tiny, individual flowers on thin, hollow stems.

They’re easy, very hardy, and with basal (ground level) foliage that is rapidly covered by other growing perennials, you won’t face the “what to do with yellowing leaves” issue that accompanies most other bulb plantings.

You can find ornamental allium in many different shades of purple, pink, red, blue and white, and in sizes that range from “wow!” to “ahh…how sweet!” Used to accent developing foliage of later bloomers, or provide the finishing architectural touch to a bed of spring favorites, allium will give your garden the professional touch you’re striving for.

When & Where to Plant Allium

Don’t make the mistake of digging a hole into hard, unforgiving soil, plopping in the bulb and then covering with rich, amended soil. Bulb roots go down – they need at least two inches of good soil beneath them.

Light: Allium thrive in full sun, but can tolerate part-shade conditions.

Soil: A well-drained soil is the most important condition for allium as bulbs may rot if left in wet soil. The average soil of most garden beds kept moist but not wet is generally fine.

Spacing: Space depending on the effect you wish to create – for single intensive plantings, space approximately 8-12” apart. For accents with larger varieties, space up to 2’ apart. While some species spread vigorously through seeds or bulbils, many varieties do not spread at all.

Planting: Plant bulbs in fall for a spring bloom. Plant dormant allium bulbs in the fall according to your growing zone. Plant them at a depth of 2-3 times their diameter (4-6”) in a well-drained sunny or partly-shaded site.

Allium is remarkably resilient in a dormant state and can wait to be planted, but needs to be in the ground a few weeks before the ground freezes in order to put down roots. If holding for any length of time, keep cool and dry in a dark location.

varieties of allium in gardenvarieties of allium in garden
Different varieties of <a href="/flower-bulbs/allium-flower-bulbs">allium</a> paired with <a href="/perennials/salvia">salvia</a> and other purple perennials make a dramatic garden statement

How to Grow Allium Throughout the Season

planting allium bulbsplanting allium bulbs
Loosen soil before planting, and make sure to give each bulb enough space to grow.
pressing bulbspressing bulbs
Fill planting hole with rich, amended soil.

Growth Habit: Think: garden lollipop. In early spring, 2-3 flat, strappy leaves will emerge from the soil and remain close to the ground. By late spring, a single hollow flower stalk (scape) will emerge, with a papery tip. The spherical cluster of flowers will emerge when the scape is fully erect, though the foliage may already have started to yellow and die back.

Staking: Allium are remarkably strong for their height, but if you live in an area with high winds, it is wise to stake individual flowers.

Watering: Evenly-moist soil is preferred during the growing season. During the dormant season, bulbs can rot if too much moisture is in the soil.

Fertilizing: A small handful of bone meal placed in the soil at planting time is a good idea for root development. After a season in your garden, mulch with compost or well-rotted manure each year for added trace nutrients and improved soil.

Mulching: Allium doesn’t require mulching, but mulching for moisture retention, nutrients and aesthetics is perfectly okay.

Trimming & Pruning: You can remove the flower clusters either when fresh or dry, but it is crucial to leave the foliage intact, allowing it to yellow and die back naturally. Many gardeners leave the flower heads in place through the autumn as they have an almost architectural appearance.

Allium: End of Season Care

close up of allium purple sensationclose up of allium purple sensation
<a href="/flower-bulbs/allium-flower-bulbs/allium-bulbs-purple-sensation">Allium</a> is an amazing attractor of pollinators, while keeping both deer and rabbit away.

If you’ve already tidied up the foliage after die back and cut off the flower scapes, there is no need to do anything more than wait for spring!

Dividing & Transplanting: Allium do not need to be dug and divided.

Pests & Disease: Insect pests are few and far between when it comes to the genus allium. Moles can dig tunnels under the roots, creating air gaps that will dry out and damage the bulb. Mice, voles and gophers will eat allium if there aren’t tulips and crocus to keep them busy.

Additional Concerns: Some species seed prolifically or create tiny bulbils in the flower head that become tiny plants. It is a good idea to check into the specific variety you are buying to make sure that this isn’t an issue.

 
  1. Purple Allium Bulbs Drumstick, Allium sphaerocephalon, Persian Onion

    In early summer Drumstick Allium ignite the garden with unique, reddish blooms that are oval shaped. One customer says it best: "Their shape adds a different dimension to any garden....

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    Drumstick Allium Flowering Onion Drumstick Allium sphaerocephalon
    $10.98 Sale $5.49
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    In early summer Drumstick Allium ignite the garden with unique, reddish blooms that are oval shaped. One customer says it best: "Their shape adds a different dimension to any garden." (Allium sphaerocephalon)
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  2. Purple Allium Bulbs Globemaster, Persian Onion

    A big Allium favorite from coast to coast. Each globe of flowers is up to 8 inches across! The purple flowers appear in early summer....

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    Globemaster Allium Persian Onion Allium
    As low as $15.98 Sale $7.99
    Per Bag of 1
    A big Allium favorite from coast to coast. Each globe of flowers is up to 8 inches across! The purple flowers appear in early summer.
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  3. Shades of Allium Bulb Collection

    Add unique, long-lasting blooms to your garden with the Shades of Allium Collection. With intriguing rounded flowerheads made up of hundreds of tiny, star-shaped florets, Allium come...

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    Shades of Allium Bulb Collection Flowering Onion Allium
    $44.98 Sale $22.49
    Per Collection of 45
    Add unique, long-lasting blooms to your garden with the Shades of Allium Collection. With intriguing rounded flowerheads made up of hundreds of tiny, star-shaped florets, Allium come into bloom in late spring and last deep into summer. This colorful mix includes 25 burgundy-magenta 'Drumstick', 10 snow white 'Graceful' and 10 bright violet 'Purple Sensation' allium bulbs. Deer resistant. (Allium)
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  4. Blue Allium Bulbs True Blue, Allium azureum or Allium caeruleum, Persian Onion

    Blue Allium caeruleum is a deep, clear blue ornamental onion that creates perfect globes of star-shaped flowers on stems only 16" tall. Its rare blue color will help attract bees and...

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    Blue Allium caeruleum Flowering Onion Allium caeruleum, Allium azureum
    $13.98 Sale $6.99
    Per Bag of 20
    Blue Allium caeruleum is a deep, clear blue ornamental onion that creates perfect globes of star-shaped flowers on stems only 16" tall. Its rare blue color will help attract bees and other pollinators to your garden. A real beauty! (Allium caeruleum)
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Gardening with Allium: Design Advice

There are so many design ideas for allium that the gardener is exceedingly spoiled for choice. As a companion plant for smaller spring bedding plants like forget-me-nots (Myosotis sylvatica) or English daisies (Bellis spp.) it adds drama to an otherwise pretty-but-plain planting.

As a repetitive planting element, it can pull together the informal structure of disparate plants in a cottage garden – creating a stronger sense of purpose for the whole.

A favorite combination is seeing large ‘Globemaster’ allium used to echo the shapes of concrete spheres sitting within planting beds in a formal garden. Equally unexpected is the sight of tall allium breaking through a sea of meadow favorites, like yarrow and ox-eye daisy.

The globe-like multi-flowered heads of allium are very popular with insects and can be used beautifully as accents in a pollinator-friendly garden.

allium drumstickallium drumstick
<a href="/flower-bulbs/allium-flower-bulbs/allium-bulbs-drumstick">Allium Drumstick</a> blooms in early summer, and provide one of a kind blooms

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