With their large fluffy heads and rich shades of purple, it’s easy to see why alliums are a garden favourite – and knowing when to plant allium bulbs in pots will give you the best chance of seeing these beauties in your garden next year.
Blooming from late spring to early summer, it’s important to know when to plant allium bulbs to get the most out of these beautiful flowers in the garden. With large, globe-like heads and long, strong stems, alliums are perfect for adding some height and depth to your garden border ideas, so you won’t want to miss the planting window.
As you are best planting allium bulbs in the ground in autumn, it is the same principle for planting allium bulbs in pots. This is everything you need to know.
When to plant allium bulbs in pots
If you’ve landed on this page, then you are no doubt wondering ‘when to plant alliums in pots’. While we’ve spilled the beans that autumn is the best time, there are the specifics you need to know.
‘The perfect moment is autumn, from late September through November. The soil’s still got a bit of warmth, the days are drawing in, and the bulbs know it’s time to settle down and root before winter,’ explains Colin Gray, managing director of Lavender Green Flowers.
‘They need that cool stretch tucked in the soil to kick-start their spring show. Plant too late and they won’t root properly; plant too early and they might sprout before the cold slows them down. Autumn really is that sweet spot in between.’
It’s important to note that not all types of alliums are suited for pots – in fact, some alliums are bulbs you should never plant in pots, such as giant allium varieties. So opt for varieties such as Allium unifolium ‘Eros’ (£8.95 at Sarah Raven), which don’t need to be planted as deeply.
Where to buy allium bulbs
Where to place your pots
If you’re planting alliums in pots this month, they can require a little extra care compared to planting directly in the ground, so it’s important to position your plants in the right place.
‘Potted alliums have less protection from winter frost and are more susceptible to waterlogging, so they do tend to have slightly different care needs,’ explains Chris Bonnett, horticulturist and owner of Gardening Express.
‘Alliums that are planted directly in the ground benefit from the natural insulation of the soil, and excess water can drain away more easily through the surrounding earth, making them a little more resilient over winter.’
‘Once you’ve planted your allium bulbs in pots, keep them in a cool, sheltered spot outside,’ says Chris. ‘Choose somewhere which will be protected from harsh winter weather, ideally in partial shade to help keep the soil from drying out too quickly.’
‘Make sure the pots aren’t sitting directly on cold surfaces – you can wrap them in some cardboard or bubble wrap to provide extra insulation when temperatures drop below 0°C. Raise the pots a little to allow excess water to drain away and prevent root rot.’
Alliums are worthy of a spot in any garden. So don’t hesitate, planting allium bulbs in pots now will ensure a gorgeous blooming garden in 2026.
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