When to plant allium bulbs for stunning purple blooms in your garden next year

Figuring out exactly when to plant allium bulbs is a must for anyone who has those vibrant globe-like flowers on their list of must-try garden ideas for next year.

Oh sure, you can buy them ready-grown from your local garden centre, but they usually retail somewhere between £10 and £15 a pop. So, yes, putting the work in and growing them from bulbs yourself is absolutely going to save you money.

Considering alliums are always a beautiful addition to garden border ideas, we can't see them going out of fashion anytime soon. Here's what you need to know...

When to plant allium bulbs

Before we get started, it's worth thinking about what type of alliums you are hoping to grow in your garden.

'Alliums are quite a broad family of plants,' says Joseph Clark of @JoesGarden fame. 'From onions, leeks and garlic, to the most amazing flowers that stand proud in any flower bed!'

Joseph Clark

As a child, Joe spent a lot of time with his great grandmother in the garden, learning about the different plants, growing fruit and veg and spotting all the animals in the garden. Nowadays, Joe utilises his abundance of innovative growing ideas to create easy and fun recipes to help his audience lead more healthy and environmentally-friendly lives (whilst also saving money). He recently launched a gardening subscription box service called ‘Garden with Joe’ which can be found here.

It's worth noting that, much as garlic and onions are among the best vegetables to sow in October, so, too, are their flowering cousins.

'The bulbs for flowering alliums are, in my experience, best planted in early to mid autumn – which for me is mid-October,' says Joseph. 'This will give them the best shot at having a longer time in bloom in the following year.'

Andrew O'Donoghue, one of the co-directors at Gardens Revived, agrees, noting that flowering alliums are best planted before the first frosts, when the soil is still warm.

Andrew O'Donoghue

RHS-trained gardener Andrew O'Donoghue set up Gardens Revived with his brother, Christopher, in 2018  to create a thriving family business. Together, they have worked on residential gardens, listed buildings and gardens, flower shows and large estates with some exceeding 70 acres – many with historical significance.

'Planting flowering alliums in October gives them ample time to establish roots over the winter,' says Andrew.

'And this, in turn, means that they should bloom beautifully from late spring to early summer.'

Once you've decided when to plant allium bulbs, be sure to find the perfect spot in your garden for them.

'Alliums are perennials, which means that they will keep coming back each year,' warns Joseph. 

'Make sure to plant them in the perfect location, and only plant healthy bulbs with the root side down – or sideways if you're unsure, as they will usually right themselves while growing.'

Best places to buy allium bulbs

Now that you've figured out when to plant allium bulbs, it's a good idea to stock up on some. Allium crisophii, with its large showy globe-like bunches of tiny flowers, is a great way to make a splash in your garden borders – while tall alliums, such as Allium stipitatum ‘Mount Everest’, will add some structure.

Late-flowering alliums, like Allium sphaerocephalon, are a great way to add coloir to your garden over the summer. And, if you have a north-facing garden, try something like Allium moly ‘Jeannine’ (it's brilliantly suited to woodland conditions).

Whichever you prefer, try shopping from the following stockists:

• Crocus has a wide variety of flowering allium bulbs
• Thompson-Morgan, too, has a plethora of allium bulbs on offer
• Sarah Raven is also a great spot to shop a variety of allium bulbs
• Finally, Amazon is a surprisingly brilliant source of flowering allium bulbs, too!

Once you've chosen your allium bulbs, all you have to do is plant them! Make a hole about four times the diameter of the bulbs, and plant smaller growing alliums 7.5-10cm apart.

Taller species, meanwhile, need at least 20cm between the bulbs. All varieties can be planted in containers, all prefer not to be planted when it's cold and wet outside – so best be quick and get yours in the ground before October ends.

Good luck...

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