FAQs: How To Plant Allium Bulbs?

Alliums, part of the garlic and onion family, add structure, colour, and elegance to any garden. These stunning bulbs reward you with tall, globe-shaped blooms that come back year after year. Whether you’re a seasoned gardener or just starting, planting Allium bulbs is easy when you know how. Growing high-quality Allium bulbs will be a breeze with the right guidance. On this page, we’ve answered all your questions about planting Allium bulbs for a beautiful spring display.

What Are Ornamental Alliums?
Alliums are ornamental flowering bulbs (often called ornamental onions), well-known for their tall stems and striking globe-shaped flowers. They bring structure, colour, and elegance to gardens from late spring through to early summer. Available in many sizes and colours, these hardy, low-maintenance plants do best in sunny spots with well-drained soil, returning year after year with minimal fuss.

What Do Allium Bulbs Look Like?
Allium bulbs are the underground storage organs of the Allium plant. They’re round or slightly oval, with a papery outer layer, similar to onion bulbs but typically smaller. The size varies depending on the variety – some are no bigger than a marble, while others can be as large as a golf ball. The firm texture and layered structure of the bulb help store the nutrients needed for growth.

What Are The Different Colours Of Allium Flowers?
Allium flowers are most often seen in shades of blue, violet, and purple, though they also come in red, pink, yellow, and white. Some varieties, like ‘Star of Persia’, produce huge blooms up to 30 cm across, while Allium ‘Gladiator’ and Allium ‘Giganteum’ are famous for their tall stems and impressive flower heads.

What Month Do Alliums Flower?
Alliums generally flower from late spring through to early summer, depending on the variety and your local climate. Bulbs planted in October tend to produce the longest and most consistent flowering period.

Where Do Alliums Grow Best?
Alliums thrive in sunny spots with well-drained soil. Taller varieties do particularly well when planted at the back of borders, where other plants can offer some support. Whether planted in garden beds or borders, Alliums love open, bright areas that allow their bold blooms to stand tall and make an impression.

Do Alliums Prefer Full Sun Or Shade?
Alliums prefer full sun and should receive at least 6 hours of direct sunlight every day. While many varieties can tolerate some light shade, they do best in bright, open spots.

What Should You Not Plant Near Alliums?
Avoid planting ornamental Alliums near shade-loving plants like Ferns, Hostas, and Epimediums, as they have very different growing requirements. You should also avoid planting ornamental Alliums next to edible Alliums to prevent confusion. In the vegetable garden, steer clear of planting Alliums near beans or peas, as they can inhibit each other’s growth.

What Looks Good Planted With Allium?
Alliums work wonderfully with many other garden favourites. They look especially striking when paired with Irises and Peonies, which complement their tall, sculptural blooms. For a softer, more romantic effect, try combining Alliums with white-flowering plants or with Nepeta, which flowers at the same time.

When To Plant Allium Bulbs in the UK?
October is the ideal month for planting Allium bulbs, as long as the soil temperature is around 15°C or cooler, but not frozen. Alliums are spring-flowering bulbs, so planting in early to mid-autumn gives them enough time to establish strong roots before the winter chill. You can plant them at the same time as Daffodils, Tulips, and Hyacinths.

Can I Plant Alliums In November?
You can plant Allium bulbs in November. In fact, October to November is generally the perfect planting window for most climates. If you live in a warmer region, you could even plant them in December or early January.

How Late Can You Plant Allium Bulbs?
Allium bulbs are best planted in October, but if necessary, you can plant them later. Late planting may result in slightly shorter bloom times, but as long as the bulbs have time to establish their roots before the ground freezes, your display will still be lovely.

What Happens When You Plant Allium Bulbs Too Late?
If you plant Allium bulbs too late, they may not have enough time to develop strong roots before winter. While healthy bulbs can still be planted as late as December, planting late often leads to smaller plants and fewer flowers.

Do You Need To Soak Allium Bulbs?
It’s best not to soak Allium bulbs before planting. Soaking can cause the bulbs to absorb too much moisture and potentially rot before they get the chance to grow. Simply plant them directly into well-drained soil and water thoroughly after planting.

How To Grow Allium Bulbs In The Autumn?
Here’s how you can plant Allium bulbs in autumn:

1. Choose a sunny spot with well-drained soil and plant before the ground freezes.
   
2. Dig holes around 15 cm deep for large bulbs and 10 cm deep for smaller ones, leaving 7 cm between each bulb.
   
3. Place each bulb with the pointed end facing upwards, then cover with soil and water well. In containers, you can plant the bulbs a bit closer together.

How Deep To Plant Allium Bulbs?
Allium bulbs should be planted at a depth that’s about 4 times the diameter of the bulb. This protects them from frost and ensures strong, upright growth. For larger bulbs, dig a hole around 15 cm deep, and for smaller bulbs, around 10 cm.

How Many Allium Bulbs Should I Plant?
For a stunning display, plant Allium bulbs close together in small groups or rows of about 10 bulbs. Space them about 8 cm apart to create a full, eye-catching cluster when they bloom. Planting in groups, rather than individually, gives your garden a more natural and impressive look.

How Many Alliums Do You Get From One Bulb?
One Allium bulb usually produces a single sturdy stem topped with one large, round flower head.

Will Dried-Out Allium Bulbs Grow?
Dried-out Allium bulbs can still grow, provided they’re firm and not mouldy. If the bulbs feel solid and plump, they’re likely to sprout once planted. However, bulbs that are soft, shrivelled, or cracked should be discarded, as they won’t recover.

Can Alliums Be Grown In Pots And Containers?
Alliums can thrive in pots and containers. Choose a deep container that allows you to plant each bulb at a depth of about 4 times its diameter. Ensure good drainage by using a pot with holes and a well-drained soil mix to prevent the bulbs from sitting in water and rotting. Avoid heavy soil.

How Long Does Allium Take To Grow?
Alliums usually take about 12 to 14 weeks to grow after planting. Once planted in the autumn, the bulbs establish roots before winter, remaining dormant until spring. As the temperatures warm, the shoots begin to emerge, and by late spring or early summer, you’ll see tall stems and globe-shaped blooms.

How To Care For Allium Plants?
Alliums are very easy to care for and don’t require much attention. Since they’re naturally drought-tolerant, they don’t need frequent watering. Plant them in a sunny spot, as they require plenty of light to grow strong and bloom beautifully. Fertilising isn’t generally necessary, but if your soil is poor, apply a balanced fertiliser in spring to support healthy growth and vibrant flowers.

What Is Eating My Allium?
If your Allium is being eaten, the most likely culprits are Allium leaf miners, onion maggots, or slugs. Allium leaf miner larvae burrow into leaves and bulbs, causing rot and distortion. Onion maggots feed on bulbs underground, while slugs tend to chew on leaves and blooms, especially at night.

What Do You Do With Alliums After They Bloom?
After Alliums finish blooming, let the leaves die back naturally, so the bulbs can store energy for the following season. Once the foliage has completely withered, and you have dried flower heads, you can cut it down to ground level. Leave the bulbs in the soil over the winter, as they’ll stay dormant until spring. Every 3 to 4 years, divide and replant the bulbs to maintain healthy growth and create new clusters throughout your garden.

Should You Deadhead Alliums?
It’s best to allow the foliage to die back naturally before removing fading foliage and spent flower heads. The leaves continue to photosynthesise after flowering, helping the bulb store energy for next year’s growth. However, if the foliage turns brown while the plant is still in bloom, it’s safe to trim away the dead leaves.

Do Alliums Come Back Every Year?
Alliums come back year after year. They’re hardy perennials, and once planted in the right environment, they’ll bloom beautifully each spring and return for many seasons. This makes them a reliable and lasting addition to any garden.

How Many Years Do Alliums Last?
Alliums are long-lasting perennials that return and bloom year after year. To keep them healthy and ensure consistent flowering, it’s best to divide the bulbs every 3 to 4 years.

Why Didn’t My Alliums Bloom?
If your Alliums didn’t bloom, it could be due to a few reasons. The most common causes include planting the bulbs too shallow, planting at the wrong time of year, or placing them in a spot that doesn’t get enough sunlight. Another possibility is poorly drained soil, which can cause bulbs to rot before they have the chance to bloom.

Why Have My Alliums Died?
If your Alliums have died, it could be due to Allium white rot, a common fungal disease that attacks the bulbs and roots, causing them to wither prematurely. Alternatively, it could be that your Alliums are dying back naturally after their blooming season.

Why Are My Allium Leaves Drooping?
If your Allium leaves are drooping, it’s most likely due to watering issues. Overwatering can cause the bulbs to sit in waterlogged soil, leading to rot, while underwatering can dry them out. Though Alliums are drought-tolerant, they still need occasional watering during long dry spells.

Why Have My Alliums Come Up Blind?
If your Alliums have come up blind—producing leaves but no flowers—it’s most commonly caused by removing the foliage too early the previous season. The leaves require time to die back naturally, so the bulbs can store enough energy for next year’s blooms. Other possible causes include planting the bulbs too shallow or damage from harsh winter frosts.

How To Propagate Allium?
To propagate Alliums, divide the bulbs every 3 to 4 years. Once the foliage has died back, carefully lift the clump from the soil and separate the smaller offset bulbs from the main one. Replant these offsets, and over time, they’ll establish themselves and grow into mature plants, ensuring a continuous, healthy display year after year.

Do Allium Bulbs Multiply?
Allium bulbs multiply over time. After planting, they usually germinate within about 12 weeks and begin to establish themselves. When grown in the right conditions, they’ll naturally multiply and form larger clumps over the course of 3 or more years.

How To Store Allium Bulbs After Flowering?
To store Allium bulbs after flowering, let the foliage die back naturally, then lift the bulbs from the soil and allow them to dry for a few days. Once dry, place them on paper in a cardboard box or paper bag and store them in a cool, dark, and dry place, such as a garage or basement. Avoid storing bulbs in plastic or a freezer, as trapped moisture can cause them to dry out or become mouldy.

Are Alliums Toxic To Pets?
Alliums are toxic to cats and dogs. They contain compounds that can cause serious health issues if eaten, even in small amounts. This includes all parts of the plant—bulbs, leaves, and flowers. If you have pets that like to dig or chew plants, it’s best to plant Alliums in areas they can’t reach to keep your garden beautiful and your pets safe.

Are Alliums Deer Resistant?
Most Alliums are deer-resistant. Their slightly garlicky scent and taste naturally deter deer, rabbits, squirrels, and other rodents from eating them. This makes Alliums an excellent choice for gardens in areas where wildlife can often cause damage.

Where To Buy Allium Bulbs?
You can buy high-quality Allium bulbs from DutchGrown, a trusted Dutch supplier known for top-sized bulbs that produce tall stems and striking globe-shaped blooms. We offer a wide selection of the best Allium bulbs in different heights, colours, and sizes—perfect for adding structure and elegance to your garden. All bulbs are shipped throughout the UK.