All About Ornamental Onions

Did you know that some onions have attractive flowers? Several species of Allium or onion are grown exclusively for their flowers instead of their bulbous structures. Ornamental onions (sometimes called alliums after the genus name) are not planted in the vegetable garden but in beds or borders with other perennial flowers.

allium in perennial border
Figure 1: Allium 'Purple Rain' planted to hide the foliage.

Flower heads on ornamental onions are usually globe-shaped (referred to as umbels) and appear in late spring to mid-summer. The diameter of the flower heads varies from that of a quarter to a volleyball. 

The flower heads of ornamental onions can be cut and appreciated in vases indoors. Many also dry well. All parts of the plant have an onion smell when crushed.  This makes them rarely browsed on by deer and rabbits.

Growing Conditions & Care  |  Species & Cultivars  |  More Information

Growing Conditions & Care

Grow ornamental onions in moist, well-drained soils.  Bulbs may rot in soggy or wet soils. 

Flowering is best in full sun, and many will tolerate part sun well.  Shady sites will produce floppy flowers.

Fertilizer is unnecessary, but a light fertilizer application every few years using an all-purpose fertilizer in early spring as the foliage emerges can be done if a soil test shows it's needed.  

Alliums purchased from the garden center grown in nursery containers can be planted like other perennials in spring or early fall.  Those started from bulbs should be planted in the fall (October).  Typically, larger bulbs are planted 6 to 8 inches deep, while smaller bulbs are planted 3 to 4 inches deep.

After bloom, the leaves of some species (in particular those grown from bulbs) will yellow and eventually die back.  Leave the foliage in place until completely brown.  Proper placement in the garden amongst other perennials can allow those perennials to grow up and mask the fading foliage (Figures 1 and 2).

Some species will prolifically reseed.  These types should be deadheaded as soon as the flowers fade to prevent seed set.  Other types do not self-seed, and the flowers dry nicely on the stalk, providing interest for the rest of the growing season.

Allium 'Globemaster' By Ruckszio AdobeStock
Figure 2: Allium 'Globemaster''


Those species and types that grow in clumps or clusters are easily divided.  Dig the clump in early spring or early fall, split into pieces, and replant.

Those species and types that grow from larger bulbs can be propagated by offsets.  Individual bulbs can be separated in the fall and used to start new plants.

All species can be propagated by seed.  Many have a specific stratification requirement (often a series of warm temperatures, followed by cold, and then warm again).  Seeds sown in the outdoor garden, such as in a nursery bed, can receive this cold treatment naturally.  Plants will be of blooming size in approximately three years, depending on the species.

Species & Cultivars 

A large number of ornamental onions are available to the home gardener. A few are listed below.

Giant Onion

For larger, softball size flowers, Allium giganteum, attracts attention in the garden. This onion has pale purple flowers in late spring on 40-inch stems.  Leaves fade soon after the flowers finish.  

'White Giant' is a white flowering form. 'Gladiator' has bluish-purple flowers that are equally as large as A. giganteum (Figure 3). They appear in early summer on 36 to 48-inch stems.

Allium Globemaster Photo by Cindy Haynes
Figure 4: Allium 'Globemaster'
Allium giganteum 'Gladiator' Photo by Cindy Haynes
Figure 3: Giant Onion (Allium giganteum 'Gladiator')


The largest flower heads, however, are often produced on 'Globemaster' (Figure 4). This cultivar is a hybrid between A. christophii and A. macleanii. The softball to volleyball size heads are composed of hundreds of tiny pinkish-purple flowers and are borne on 24 to 36-inch stems. 'Globemaster' blooms in early summer.  This cultivar was originally developed in Holland as a cut flower.  It is one of the most reliable and impactful alliums you can plant in the garden.

Persian Onion

Allium aflatunense 'Purple Sensation' produces violet-purple flower heads the size of a baseball (Figure 5). Flowers appear in late spring or early summer on 20 to 30-inch stems.  Foliage dies back soon after the flowers fade.

Allium karataviense 'Ivory Queen' by Cindy Haynes
Figure 7: Turkistan Onion (Allium karataviense 'Ivory Queen')
Allium cristophii By Alexandra AdobeStock
Figure 6: Star of Persia (Allium christophii)
Allium aflatunense 'Purple Sensation' by Aaron Steil
Figure 5: Persian Onion (Allium aflatunense 'Purple Sensation')

Star of Persia

Allium christophii has attractive large 10 to 12-inch flower clusters on 12 to 20-inch stems (Figure 6). Amethyst purple flowers appear in late spring, often last for 2 to 3 weeks, and then dry a silvery-tan color with little or no effort.  The foliage of this species tends to die before the flower fully open.

Turkistan Onion

Allium karataviense is another ornamental onion with attractive foliage. The gray-blue foliage serves as a colorful backdrop to the lilac-colored flower heads before they disappear in late summer. The golf ball-sized flower heads are borne atop 8 to 12-inch tall stems and dry a silvery-tan color with little or no effort.  Plants are some of the shortest statured on this list.

'Ivory Queen' is only 6 inches tall with whitish flowers in late spring. Its attractive, dark green leaves complement the baseball-size flower heads (Figure 7).

Allium 'Summer Beauty' close up by Aaron Steil
Figure 10: Allium 'Summer Beauty' 
Allium Serendipity by Cindy Haynes
Figure 9: Allium 'Serendipity'
Allium Hybrid cvs Photo by Cindy Haynes
Figure 8: Allium Hybrids

Hybrid Ornamental Onion

There are several clump-forming hybrid alliums commonly available at garden centers (Figure 8).  These ornamental onions are most typified by the cultivar ‘Millenium’ (yes, there is only one "n" in that cultivar name!). Abundant two-inch globe-shaped lavender-purple umbels of flowers appear in mid to late summer above a compact upright clump of glossy green, thick, and strappy leaves.  These leaves persist all season, unlike other alliums that grow from bulbs.  

Newer introductions that are similar include, 'Serendipity' (sport of 'Millenium' with blue-tinged foliage) (Figure 9), 'Lavender Bubbles' (later blooming than 'Millenium' with darker and slightly larger umbels), 'Bubble Bath' (lighter colored flowers than 'Millenium' with slightly larger umbels), and 'Summer Beauty' (A. lusitanicum, lavender flowers, sterile) (Figure 10). 

Drumstick Onion

Drumstick allium (Allium sphaerocephalon) has small (quarter-size) flower heads in early summer (Figure 11). The flowers are maroon at the base and fade to purple near the top. Leaves strongly resemble those of chives and can grow 2 to 3 feet tall.  Drumstick allium frequently reseeds and forms small colonies in suitable sites.

Allium caeruleum by aleks22n AdobeStock
Figure 12: Blue Globe Onion (Allium caeruleum
Allium sphaerocephalon By Alexandra AdobeStock
Figure 11: Drumstick Onion (Allium sphaerocephalon)

Blue Globe Onion

Allium caeruleum (azureum) has clear, blue, quarter-size flower heads in early summer (Figure 12). The 12 to 18-inch tall plants freely reseed and naturalize in sunny, undisturbed areas.  Foliage persists into summer.  Plants need exceptionally well-drained soils to thrive.

Nodding Onion

A North American native, nodding onion (Allium cernuum), has a unique nodding umbel of lilac-pink flowers that appear in early summer (Figure 13).  The foliage gets approximately 18 inches tall and persists into late summer.  If self-sowing becomes an issue, deadhead immediately after flowering.  

Allium schubertii By Alexandra AdobeStock
Figure 14: Tumbleweed Onion (Allium schubertii)
Allium cernuum by Danny AdobeStock_357598341
Figure 13: Nodding Onion (Allium cernuum)

Tumbleweed Onion

Another giant flowering onion is Allium schubertii (Figure 14). The loose and open flower clusters almost resemble fireworks exploding and appear in late spring on 12 to 24-inch stems. They approach the size of volleyballs. Individual flowers are rosy purple.  The foliage dies back soon after the flowers fade.  The umbel dries nicely and eventually breaks off near the ground and rolls away in the wind.

Golden Onion

The bright yellow flowers of Allium moly are unusual for the onion family (Figure 15). The golf ball-sized flower heads appear in early summer on 10 to 12-inch stems. This onion is aggressive and freely naturalizes in undisturbed areas.

Allium moly photo by Cindy Haynes
Figure 15: Golden Onion (Allium moly)

More Information

Photo credits: Figure 1: Aaron Steil  |  Figure 2: Ruckszio/AdobeStock  |  Figure 3: Cindy Haynes  |  Figure 4: Cindy Haynes  |  Figure 5: Aaron Steil  |  Figure 6: Alexandra/AdobeStock  |  Figure 7: Cindy Haynes  |  Figure 8: Cindy Haynes  |  Figure 9: Cindy Haynes  |  Figure 10: Aaron Steil  |  Figure 11: Alexandra/AdobeStock  |  Figure 12: aleks22n/AdobeStock  |  Figure 13: Danny/AdobeStock  |  Figure 14: Alexandra/AdobeStock  |  Figure 15: Cindy Haynes

Last reviewed:
May 2024