How to Plant & Grow


Also known as ‘Ornamental Onions’, Alliums are an impressive summer plant that will offer plenty of colour and excitement to your seasonal displays. With many popular alliums being winners of multiple awards, it’s safe to say that this bloom will take your summer garden to a whole new level!


If you’re new to gardening or new to planting Alliums, then we’re here to help. Follow this handy guide to get you from A to B, as well as essential advice for maintaining their gorgeous blooms throughout the season and beyond. 

What We've Included

How They Will Arrive   |   When to Plant   |   Where to Plant   |   How to Plant   |    When will they flower

   |   After Care   |   Common Issues 

How They Will Arrive

Our allium bulbs will be delivered fresh and healthy. There should be firm, not soft. Some bulbs may arrive with slight mould patches, but this is completely normal and can be brushed off. If you suspect that your bulbs are faulty, do not hesitate to get in touch.

We measure our allium bulbs by circumference rather than diameter. The bigger the bulb, the bigger the bloom! For large-flowering varieties like Globemaster, these are the biggest bulbs we supply, averaging at 18-20cm or 20cm+ circumference.

Once your bulbs arrive, take them out of their packaging and lay out in a box so they can breathe. Put into a paper or mesh bag for storing. This is so they don’t excessively sweat in their containers, ruining the bulbs. 

When to Plant

Some gardeners say that Allium bulbs prefer to be planted in early to mid-autumn, often between September and October. However, in the UK, you can plant right up to the end of January (frost allowing your hole digging).  Some Allium varieties are even sold and can be planted in the spring. If you receive your bulbs from us before then, store them in a cool and dry place so they remain in perfect condition.

Quick tip: Although they will tolerate any soil type, they will rot when planted in water-logged areas. Grow your bulbs in a sunny position and ensure the soil is well-drained before planting.

Where to Plant

Allium bulbs can be planted in beds and containers. Many Allium varieties are quite tall compared to other seasonal blooms, making them a great choice for adding height to the back of your beds.


Grow your bulbs in areas that reach some sunlight but aren’t exposed to harsh weather conditions. This could risk them getting blown over, ruining their chances of survival.


If you worry about a lack of sunlight exposure in your garden, flowerpots can be incredibly helpful. Simply move them to wherever the sun is positioned! 

How to Plant


1. Dig a hole that’s wide enough to fit the bulb comfortably, and at least 4 times the bulb’s depth (around 15cm). Smaller alliums can be planted in groups with less space between them, but alliums like ‘Globemaster’ need extra spacing as their heads are so large. 

2. Pop each bulb into the hole, pointed side up. Smaller bulbs can be planted 7-10cm apart, and larger bulbs should be spaced around 20cm apart.

3. Cover with soil and pat down gently. Do not step on the area, as it can damage the bulbs.



1. Fill the pot with any peat-free compost until you’ve reached its halfway point.

2. As a rule of thumb, bulbs should be planted as deep as you would plant them in borders, as they can be quite tall and need a good anchor.

3. Place your bulbs on top of the soil and cover with the compost to the top of the pot. Break up any lumps as you go.

4. Gently press the soil so that it’s nice and flat.

5. Make sure you place your pot on feet to allow the moisture from the pot to escape.


Note: Although alliums can be planted and enjoyed in containers, they must be planted in a deep pot.

Watch Our Videos On How to Plant Alliums

Watch: How to Plant Allium Globemasters

Watch: How to Plant Allium Sensation

When will they flower?

Once planted in early-mid autumn, most alliums will appear from as early as late spring. 

Early Alliums
Appearing from May and June, these early-flowering alliums are perfect for joining the spring garden to your early summer displays. From varieties like Allium karataviense to Purple Sensation and Mt. Everest, these blooms will add plenty of colour and height to your borders.

Mid-Season Allium
These blooms will often appear mid-season. Although they should be planted at the same time as other varieties, their blooms will appear from early summer. A few of our favourite mid-season varieties include the ever-impressive Graceful Beauty and Globemaster.

Late Alliums

Late-flowering alliums are the last to appear in the season, lasting to early autumn. These blooms are perfect for adding colour to the garden when your other plants and flowers are starting to die back after a floriferous bloom. Allium nigrum, or black garlic, is a notable late-flowering variety that will provide gorgeous blooms from June and July. 

Always check the flowering information on our product pages before buying, as it will indicate what months that specific plant or flower will appear.

After Care

When to water
As long as the soil is moist, there’s no need to water your alliums as they are incredibly drought tolerant. However, if you’ve planted your bulbs in containers, they will need regular watering. Aim for once a week if the weather is unseasonably warm.



It’s not necessary to deadhead allium flower heads, as it won’t affect their regrowth the following year. Spent allium heads also look fabulous through the autumn and winter, giving you a few more months of texture to the garden.


Propagating Alliums

Although not completely necessary, Allium bulbs can be lifted and replanted. This is because many varieties produce offsets which are essentially brand-new baby bulbs.


In late autumn, carefully lift the bulbs (try not to damage the bulb or they won’t re-grow) and divide them carefully from the original. You can then replant these into the soil, just like you did with your first batch.


What to do once they’ve finished blooming

One of the best reasons for choosing to grow many Allium varieties is the evolution of Flowers to seed heads.  Beautiful colourful flowers evolve to striking seed heads through late summer and Autumn which gives you fabulous structure in the garden for many months.

As alliums are so hardy, they won’t need extra care through the winter. However, if you plan on keeping your bulbs in containers, then these could be more susceptible to harsh weather conditions.


To avoid bulb damage, move your containers to a well-sheltered area of the garden, out of the way from rain and harsh wind.


Lastly, but most importantly: do not cut back their foliage, even if it’s turned a golden-brown colour. Although it is tempting, especially to neaten up your beds, it will interrupt the photosynthesising process and will damage the bulb’s ability to re-grow the following season.

Common Issues and How to Solve Them

Allium White Rot
Unfortunately, some ornamental alliums can suffer from a disease called Allium white rot. This fungal disease may present itself in a myriad of symptoms, such as yellow wilted foliage and the decaying of bulbs and roots. The only way to avoid this disease is to ensure you’re not transferring soil to soil via tools or shoes. If you discover this disease on your bulbs, remove them and avoid planting more in that area, as the disease will still be there. 


Allium Leaf Miner 
The Allium leaf miner is a type of fly that love onion and leek plants. Symptoms of the Leaf Miner include the appearance of greyish-brown flies, the presence of white larvae, and the rotting of the plant due to infection. Unfortunately, there aren’t any pesticides that can control the infestation. The best course of action is to lift the bulbs in their entirety and burn the remains.