How to Plant and Grow Allium

Because the perennial plant allium has relatively unobtrusive foliage that blends in quite well with surrounding plants, they’re easy to mix and mingle with other plants in the garden. Depending on the species and cultivar, they’re hardy in zones 4-9. Allium is easily recognized by its big, round head of flowers, though some types may be less showy than others. In addition, their onion smell is a powerful deterrent to hungry animals.

Where to Plant Allium

For the most productive display of blooms, plant alliums in full sun. This will assure sturdy stems, so flowers will be less likely to flop. Some of the giant varieties can benefit by being planted near a wall or fence for some protection from strong winds, so you won’t have to worry about your blooms snapping in a storm. Some varieties may tolerate part shade but perform best in full sun. Avoid soggy soil or locations that don’t drain well.

Their scent and taste deter deer and other animals, so try planting some at the front of garden borders or surrounding tender lily bulbs.

How and When to Plant Allium

Plant allium bulbs in fall for late spring or early summer blooms. Plant them at a depth of 2 to 3 times the diameter of the bulb and water well.

Alliums make great additions to gravel gardens, and dwarf varieties also make great accents in troughs and small containers.

Allium Care Tips

Very little maintenance is required for allium to grow and thrive.

Light

Get as much growth and as many flowers out of your allium during their short season by planting them in full sunlight.

Soil and Water

Because alliums generally form bulbs, they need well-drained soils. If their bulbs sit in water, they’ll rot.

The fact that most alliums are bulbs works to their advantage. By storing water and nutrients, these plants are extremely drought tolerant and can survive long dry spells that might kill other plants without the benefit of a storage root. If you get plenty of rain, there’s no need to water allium – if you don’t, water every three to five days.

Temperature and Humidity

When you choose allium plants, check their hardiness in your zone. Most are hardy in zones 4-10, so will do fine in a range of temperatures.

Fertilizer

Add balanced fertilizer when your plants first start flowering. Otherwise, they don’t need fertilizer in most soil.

Pruning

When allium has finished blooming, removing spent blooms can encourage the plants to store more energy for next year’s show, but it isn’t necessary. Leaving the old flowers on can add interest and encourage re-seeding if you’re hoping to increase the number of allium plants in your garden.

Potting and Repotting Allium

Allium grown in pots will need repotting as it outgrows its containers. In autumn, dig out the bulbs of the plants and divide where needed. Replant in pots that are well-draining, or add divided bulbs to in-ground gardens before the first frost.

Pests and Problems

There are very few pests or problems with alliums. Because alliums belong to the onion clan, these blooms are associated with that trademark odor. This smell works as an animal deterrent and, coupled with their taste, prevents alliums from being eaten by creatures like pesky rabbits, deer, and other browsing animals. Many gardeners take advantage of this and plant them among other plants to act as a barrier to troublesome critters.

How to Propagate Allium

Alliums don’t require dividing, so there’s no need to dig them in the fall. However, if you want to divide them and plant them in other locations, you can.

Types of Allium

The variety of allium colors, shapes, and sizes makes them easy to use. The colorful balls of blooms are composed of numerous smaller flowers to create Dr. Seuss-like displays of lollipops throughout the garden. There are also many allium varieties that have flat-topped or domed blooms that can add a nice geometry to garden designs. Other varieties still have more explosive blooms reminiscent of fireworks throughout the garden.

Allium aflatunense

Allium aflatunense features big, spiky flower heads packed with purple blossoms on thick stems in late spring. It grows 30 inches tall. Zones 4-8

Allium carinatum pulchellum

Allium carinatum pulchellum blooms in late spring, showing off clusters of nodding reddish-purple flowers on 2-foot-tall stems. Zones 5-8

Allium cyathophorum var. farreri

Allium cyathophorum var. farreri is a vigorous selection with clusters of deep violet-purple flowers in summer. It grows 1 foot tall. Zones 4-9

Allium schoenoprasum

More commonly known as chives, this traditional herb is grown more for its tasty foliage than its purple blooms. Zones 4-8

Allium schubertii

Allium schubertii is one of the most dramatic alliums. It shows off volleyball-size clusters of lavender flowers on 2-foot-tall stems. Zones 4-10

Allium oreophilum

Allium oreophilum is a tiny star for the rock garden. This petite onion features airy clusters of rosy flowers on 4-inch plants. Zones 4-7

Allium senescens subsp. montanum var. glaucum

Allium senescens subsp. montanum var. glaucum is perfect for the rock garden or front of the border. It has blue-green leaves that grow in a spiral and clusters of purple-pink flowers in late summer. It grows 6 inches tall. Zones 5-9

Allium stipitatum

Allium stipitatum blooms in early summer with 4-inch-wide clusters of lilac flowers. It grows 4 feet tall and is sometimes confused with the similar showy allium. Zones 4-9

Allium tuberosum

Another tasty allium, garlic chives are not quite as commonly used as standard chives. These have a flat leaf blade, where standard chives are hollow tubes. White blooms are borne in early summer. Zones 4-8

Allium triquetrum

Allium triquetrum bears clusters of drooping white bells that flourish in partial shade and will spread in moist soils. The flowers unfurl in late spring on 18-inch-tall stems. Zones 3-9

Giant allium

Allium giganteum is one of the largest varieties. It bears large globe-shaped clusters of purple flowers on 6-foot-tall stems. Zones 5-10

Bear’s garlic

Allium ursinum is noted for its 2-inch-wide shaggy white flower heads that appear on 18-inch-tall stems in summer. Zones 4-9

Blue allium

Allium caeruleum delights with airy bunches of delphinium-blue flowers on 18-inch-tall stems in late spring. Zones 5-7

Drumstick allium

Allium sphaerocephalon offers egg-shaped reddish-purple spheres in early summer on 2-foot-tall stems. Zones 5-9

‘Gladiator’ allium

Huge stalks reaching 4-5 feet tall are topped with softball-size purple blooms in early summer. Zones 4-7

‘Globemaster’ allium

Allium ‘Globemaster’ is a dramatic selection with 10-inch violet flower heads on 3-foot-tall stems in late spring to early summer. Zones 4-9

Golden garlic

Allium moly produces bunches of star-shaped, bright yellow blooms that spread their sunshine in rock gardens in late spring to early summer. It grows 12 inches tall. Zones 3-8

‘Hair’ allium

Allium ‘Hair’ is the most unique allium. Rather than petals, this plant bears spidery green leaves atop its 18-inch-tall stems in late spring. Zones 4-8

‘Ivory Queen’ allium

Allium karativiense ‘Ivory Queen’ shows off 6-inch orbs of white flowers over wide, blue-green foliage. It grows 10 inches tall. Zones 5-8

‘Millenium’ allium

Allium ‘Millenium’ features 2-inch-wide lavender-rose flower spheres above clumping green foliage for several weeks in late summer. It grows 12 inches tall. Zones 5-8

‘Mount Everest’ allium

Allium ‘Mount Everest’ bears tennis-ball-size white flowers on 4-foot leafy stems. Zones 4-9

Naples garlic

Allium neapolitanum is a summer-blooming species that has 2-inch-wide clusters of white flowers. It grows 16 inches tall. Zones 6-10

Nodding onion

Allium cernuum is a North American native with clusters of pink flowers in summer on 2-foot-tall stems. Zones 4-10

‘Purple Sensation’ allium

Allium aflatunense ‘Purple Sensation’ bears giant violet flower globes that radiate whimsy and cheer on 3-foot-tall stems in spring. Zones 4-8

Showy allium

Allium rosenbachianum offers 4-inch-wide globes of purple flowers in summer. It grows 3 feet tall. Zones 4-10

‘Silver Spring’ allium

Allium ‘Silver Spring’ bears clusters of white flowers marked with a red-purple eye. This dramatic selection blooms in early summer and grows 2 feet tall. Zones 4-8

Star-of-Persia

Allium cristophii bears distinct silvery-lavender flower globes measuring 12 inches in diameter atop tall 2-1/2-foot stems in late spring. Zones 4-9

‘Summer Beauty’ allium

Allium tanguticum ‘Summer Beauty’ shows off clusters of dark lavender-blue flowers in midsummer on 2-foot-tall stems. Zones 4-9

‘Summer Skies’ allium

Allium tanguticum ‘Summer Skies’ bears lavender-blue flowers in midsummer on 2-foot-tall stems. Zones 4-9

Turkestan onion

Allium karataviense bears loosely clustered red-and-white flowers on 10-inch-tall stems in late spring. Zones 4-8

White giant allium

Allium giganteum ‘Album’ is a white-flowering version of giant allium. It grows 6 feet tall. Zones 5-10

Companion Plants for Allium

Cabbage

Plant allium with vegetables to keep critters from eating your plants. The scent and taste of allium repel animals. Allium keeps cabbage loopers and other vegetable-eating insects away from plants.

Phlox

Phlox, whether tall or low-growing varieties such as sweet william, have the same soil and sun requirements as allium, and their smaller flowers complement the large allium pom poms.

Yarrow

This rugged perennial works in both cottage and wildflower settings.