How Late Can you Plant Allium Bulbs?

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You can find ornamental alliums (ornamental onions) for fall planting at the garden center in late summer. But what happens if you don’t get your allium bulbs in the ground in the fall? Can you plant them in spring? How late can you plant allium bulbs in the ground and still have healthy plants that come back year after year? We have answers to all these questions, plus we tell you how to best plant and care for your allium bulbs to ensure they keep coming back!

Purple allium flowers in bloom outdoors.

How to Care for Allium Bulbs

Allium sphaerocephalon are flowering ornamental perennials that add whimsy, texture, and color to garden beds. These low-maintenance members of the onion family are hardy bulbs that make a great addition to perennial gardens.

Taller varieties of alliums look beautiful at the back of the border. Smaller varieties you can plant at the front of the border for show-stopping pops of purple flowers with perfect spherical blooms.

  • Hardiness zones: Alliums can be grown in USDA zones 3 to 9. Not sure which zone you’re in? Check here!
  • Sun requirements:  Plant in full sun to partial shade
  • Frost Tolerance:  Excellent frost tolerance for all the ornamental onions.  Plants are hardy to -25F to -32F.
  • Soil Requirements:  Alliums require good drainage with fertile soil. Plants will tolerate clay soils and sandy soils. Do not plant in areas where there is standing water after rainfall.
  • Water requirements:  Water when planted, and moderately through spring. 
  • Feeding Requirements: The best time to fertilize your alliums is early spring when new growth emerges.  Top dress with compost. You can also use a liquid fertilizer in early summer when the plants have full leaves. 
  • Bloom time:  Allium blooms from early summer to late fall depending on planting time and cultivars.

Learn More: For more information on growing alliums, check out our full guide to growing popular ornamental allium varieties!

Tip for Hiding Spent Allium Flowers

Alliums look beautiful when in bloom, but their flower heads can look messy as they start to fade—plant bushy summer flowering perennials in front of your alliums to prevent your gardens from looking disheveled.

A giant allium bloom on a white background.

How late can you plant allium bulbs?

It’s probably not too late to plant your allium bulbs if it is still Spring in your area!

Although bulbs planted in the fall will put on a spectacular show the following year, you can plant allium bulbs in the spring.   

Anytime the ground is workable, and you can dig deep enough, you can add allium bulbs to your garden.

With that said, fall-planted blooms will do best in their first year.  First-year flowers from bulbs planted in spring may be thin, possibly may not bloom, and will not be as robust as flowers planted in fall.  Or plants may not bloom until late summer or early autumn.

They will, however, flower abundantly the following spring.  

If you didn’t have time to get those bulbs in the ground in the fall, it’s not too late!

Related: For more information on fall-planted bulbs, check out this guide!

Allium Planting – Early Winter Planting isn’t Recommended.

Although you can plant your allium bulbs in fall and spring, you need to avoid planting them in early winter. Early winter planted bulbs will not have enough time to root well and may die when the ground freezes.

Giant allium in bloom in the garden.

How to plant allium bulbs

  • Planting time:  It is best to set out dormant bulbs in the fall.  Wait until the soil is 60F or colder.  In the North you can plant in September or October, in the South you can wait a bit longer and plant in mid-fall to late fall in October and November.  You CAN plant your alliums in late spring – the first-year blooms may not be as spectacular, but the plants will keep coming back.   
  • Depth:  Cover the bulbs to four times their depth with loose soil.  Be sure to plant the pointy end up.   Allow 12″ between bulbs of most varieties.  Smaller bulbs and varieties can be planted closer together.
  • Spacing: 8″-12″ inches apart. 
  • Flower Care: After the flowers have bloomed do not cut off the foliage. The foliage must remain so the bulbs can have enough time to store food for next year’s blooms. You can remove the foliage once it has turned yellow and died back completely.

Related: Looking for more flowers to grow from bulbs? Try growing crocus flowers with our complete guide.

Use Alliums as Garden Punctuation!

Note: Alliums are like beautiful purple exclamation points in the garden. Use them to help move the eye through the garden by scatter-planting them through the borders and beds. Or use alliums to punctuate a single display you want to bring attention to.

Pests & Diseases of Allium Flowers

Alliums generally have few pests. They make good companions for other vegetables and flowers, including roses. However, they are susceptible to whitefly.

The plants can be susceptible to fungal diseases like white rot and downy mildew. Preventative measures go a long way to help prevent these diseases from taking hold.

Be mindful of the planting distance between bulbs. Avoid overplanting as it can lead to poor air circulation, which will create an environment where fungal diseases can start. You will also want to ensure your bulbs have excellent drainage as the bulbs do not like sitting in water and will rot.

Harvesting Allium Flowers for Cut Flower Arrangements & Dried flowers

When using allium flowers in cut flower arrangements, be sure to make a clean cut with a sharp, sterile knife—Harvest when only a quarter to half the florets is open.  

Alliums will last 4-7 days. Recut stems just before placing them in cold water to condition overnight.

For drying, cut flowers when they are about three-quarters open. Tie in bundles and hang to dry in a cool, dark room.

Learn More:

Do Alliums Smell like Onions? No!

Allium flowers don’t smell like onion or garlic at all. Instead, many smell like light lilac or have a faint pleasant sweet smell. However, when bruised, their leaves and stems can give off an oniony scent.

So don’t worry about using alliums in your cut flower arrangements; they will not be stinky at all!

Allium types to try in your gardens

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It’s not too late to plant allium bulbs in your garden! You may be considering adding these beautiful flowers to your garden this year, and you might be thinking it’s too late – but it’s not!

Here are a few of our favorites:

Try the tall Allium giganteum (giant allium)Kids LOVE these giant lollipop-looking flowers. They seem so magical and otherworldly, almost comic book-style flowers.

  • Globemaster
  • Gladiator
  • Mount Everest

Other types to try:

  • Purple Sensation Allium – will self-sow and spread slowly around the border.

Look for these at reputable garden centers.

The Best Books For Bulb Planting

The best gardening books we have found so far for bulbs are the following:

The Gardeners Guide to Bulbs by Kathy Brown- Comprehensive information about bulb growing. I dislike the small tiny print, and I hate that the book only uses the Latin names of flowers but it is a solid reference book.

Favorite Bulbs by Lois Hole – I love all of Lois Holes’s books for their ease of reading. Her layouts are always fantastic, and her information is laid out perfectly so you can find what you are looking for quickly.

A pink allium flower on a white background.

Are you learning about bulbs and want more Free information?

We have you covered! Grow gorgeous gardens with bulb plantings – if you’re anything like me, you will become infatuated with collecting and growing bulbs year after year.

Do alliums come back every year?

Yes! Alliums are perennials that will come back every year. They are very cold hardy, so they will survive winters in most zones.

Will allium bloom if planted in spring?

Yes, spring planted allium will still bloom. The blossoms won’t quite be as large, but they will come in at full strength the following year.

What happens if you plant bulbs too deep?

If you plant allium too deep you may get just foliar growth with no flowers, or no growth at all. Try to plant allium at 4 inches below soil surface to ensure best growth, and reduce the chance of shallow bulbs being dug up by critters.

Can I transplant allium bulbs in the spring?

Allium bulbs should not be transplanted in the spring. Wait until late summer, when the foliage starts to yellow, so that the plant is going into dormancy and is not focussed on new growth. Be sure to dig them up before the stems wilt away completely, or it will be tough to find the bulbs!