Allium 'Millenium'. Photo by: Proven Winners

With names like ‘Gladiator’, ‘Goliath’, and ‘Globemaster’, there’s no doubt about the powerful punch ornamental onions can pack. The globe-shaped blooms are comprised of hundreds of densely packed individual flowers. They also make chic pairings with a plethora of other perennials and even lend a touch of humor.

We find killer combinations of qualities in ornamental onions: easy and gorgeous, elegant and playful, dainty and bold, at home in both meadows and formal borders. Perfect “tuck-ins,” they play well with other plants, and return reliably year after year. With lots of colors, heights, and sizes, there are alliums for every garden, small or large. They also make outstanding, long-lasting cut flowers.

On this page: Basics | Planting | Care | Varieties | Design Ideas

On this page:

THE BASICS

Botanical name:

Allium spp. Onions, chives, garlic, and leeks also belong to the genus Allium.

Common names:

Ornamental onion

Zones:

3-8, depending on variety

Height/spread:

12 to 36 inches tall, 3 to 18 inches wide, depending on variety

Exposure:

Most prefer full sun—even part shade will make them lean over, reaching for the light. But a few species, such as nodding onion, garlic chives, and Allium karataviense can take a bit of shade.

Bloom Time:

Early summer, just as spring bloomers are winding down and will continue until summer bloomers kick into gear.

Allium flowers:

Most are purplish-pink, they also come in white, blue, and yellow.

Are alliums deer resistant?

Close cousins to onions and garlic, deer are deterred by their scent.

PLANTING ALLIUM BULBS

Allium caeruleum bulbs. Photo by: Max_555 / Shutterstock

When to plant:

Plant in fall, a few weeks before the ground freezes.

How to plant:

Plant allium bulbs twice as deep as the bulb is tall, with the pointy end up.

Soil:

Generally tolerant of soil type; the important thing to remember is they must have well-drained soil. Avoid wet locations, especially during their dormant period, which can lead to rotting.

Can alliums be grown from seed?

They can be grown from seed, but hybrids won’t come true and you may end up waiting a year or more for them to bloom.

Learn more about planting and caring for flower bulbs.

ALLIUM CARE

Watering:

During the growing season, provide alliums with evenly moist, but not soggy, soil. Cut back watering in the dormant season when too much water can cause rot.

Fertilizing:

Add bone meal to the planting area at the time of planting. In following years, add a layer of compost to keep soil healthy.

After blooming:

Allow foliage to die back naturally; don’t cut it off while still green since it feeds the bulbs and sets them up for a successful flower display the following year. To avoid seeing fading bulb foliage, plant among perennials that require similar conditions.

Staking:

Although their stems are strong, taller varieties should be staked if planted in windy areas.

Pests and diseases:

Alliums are virtually pest-free and will even repel garden pests such as aphids. However, thrips can be problematic occasionally. They also attract beneficial insects such as bees, parasitic mini wasps, and hoverflies that help keep insect pests under control.

TYPES OF ALLIUMS

Swipe to view slides

Photo by: Proven Winners

'Serendipity'
Allium hybrid

Zones: 4-8

Height/spread: 15 to 20 inches tall, 10 to 15 inches wide

This award-winning hybrid variety is easy to grow in either full sun or partial shade, in any type of soil.

Photo by: Proven Winners

Allium 'Millenium'

Zones: 4-8

Height/spread: 12 to 18 inches tall & wide

This later-blooming variety (July-August) will appreciate some light afternoon shade in warmer climates.

Photo by: LapalirKrapai / Shutterstock

Allium giganteum
Giant onion, giant allium

Zones: 5-8

Height/spread: 3 to 5 feet tall, 1-1/2 to 2 feet wide

Shelter this taller variety from strong winds or provide staking for support.

Photo by: sharohyip / Shutterstock

Allium 'Gladiator'

Zones: 4-8

Height/spread: 3 to 5 feet tall, 1-1/2 to 2 feet wide

Six-inch-wide flower heads wide bloom on stems up to 5-feet tall in June to July. Best planted in groups of 10 or more.

Photo by: Rob Cardillo

A. sphaerocephalon
Drumstick allium

Zones: 4-8

Height/spread: 24 to 36 inches tall, 12 to 18 inches wide

Drumstick allium makes a good companion for shorter perennials, or as a see-through front of the border plant.

Read more about drumstick alliums.

Photo by: skyfish / Shutterstock

A. moly
Lily leek, golden garlic

Zones: 3-9

Height/spread: 9 to 18 inches tall, 6 to 9 inches wide

A unique yellow allium with star-shaped yellow flowers that bloom in loose clusters. To help control spread, deadhead flowers before they go to seed.

Photo by: Rob Cardillo

A. cristophii
Star of Persia

Zones: 5-8

Height/spread: 12 to 24 inches tall, 6 to 18 inches wide

Volleyball-size flower heads add drama when emerging through low-growing perennials. Flower heads dry well, like fireworks frozen in time.

Photo by: Rob Cardillo

Allium 'Mount Everest'

Zones: 4-8

Height/spread: 24 to 36 inches tall, 9 to 12 inches wide

Six-inch snowballs of flowers bloom in late spring to early summer. Low-growing foliage doesn’t die back during flowering, making a green groundcover under the blooms.

Photo by: Rob Cardillo

A. unifolium
Oneleaf onion

Zones: 5-8

Height/spread: 1 to 2 feet tall, 3 to 4 inches wide

West Coast native with half-dollar-size flower heads that bloom May to July. More moisture tolerant than other alliums, found in wild grasslands that are damp during the spring. Be prepared for it to spread and naturalize.

Photo by: Rob Cardillo

A. hollandicum 'Purple Sensation'

Zones: 4-8

Height/spread: 24 to 32 inches tall, 12 to 18 inches wide

Hundreds of purplish flowers are packed into perfect baseball-size globes—a classic ornamental onion. A great cut flower, it can last three weeks in a vase.

Photo by: Rob Cardillo

A. cernum
Nodding onion, lady's leek

Zones: 5-8

Height/spread: 12 to 18 inches tall, 3 to 6 inches wide

A summer-blooming North American wildflower, native to dry open woods and meadows. Flower stalks have a distinctive crook at the end, so the flowers hang downward.

Photo by: Rob Cardillo

A. caeruleum

Zones: 5-8

Height/spread: 12 to 24 inches tall, 6 to 12 inches wide

This uniquely blue allium blooms in June and July with half-dollar-size flower heads. Naturalizes in the garden in a welcome, not weedy, way.

DESIGNING WITH ALLIUMS

Allium 'Globemaster'. Photo by: Rolf E. Staerk / Shutterstock

  • Alliums make great “mixers” among other border plants, and many can be planted to come up through lower-growing perennials like Nepeta x faassenii and Geranium sanguineum, which also hide fading bulb foliage.
  • Since alliums are perennial, they can be integral elements in a longterm design that gets better as it matures.
  • The consistency of height and flower-cluster size in a single species make alliums a perfect plant for repetition in the garden or as a focal point when closely planted in groups of 5 or more.
  • Ornamental onions offer a variety of heights, colors, and bloom times, so you can sprinkle a lot of different types throughout the garden. They can also serve as bridge plants, helping the garden transition from spring into summer.
  • The combination of long stems and spherical flower clusters, swaying and nodding in the breeze, adds three-dimensionality to the garden. Plant with sturdy architectural plants like phlomis and tall sedums for textural counterpoint.
  • Combine alliums with grasses such as fountain grass, and herbs like lavender for a deer-resistant garden.

RELATED:
More Bulbs for Your Garden
20 Best Summer Bulbs to Grow
Top 20 Spring-Blooming Bulbs
21 Easiest Flowers for Beginners

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