With their gorgeous globe-shaped flowerheads held high above borders, alliums are one of the stars of late spring and early summer gardens. But once those colourful blooms begin to fade, many gardeners are left wondering whether they should cut them back or leave them be. Thankfully, alliums are easy to care for after flowering – and a little patience can help ensure even better displays next year.
Whether you prefer a tidy outdoor space or enjoy the beauty of seed heads through autumn and winter, here's what to do once alliums have finished flowering.
1. Leave the flowerheads for extra interest
Unlike many flowering plants, alliums can continue to earn their place in the garden long after their blooms have faded.
‘After alliums have flowered, you can leave the flowers to their own devices,’ says Richard Barker, horticultural expert and commercial director of LBS Horticulture. ‘The flowerheads will die back naturally, and they will continue to add height, texture and interest to your garden.’
Many gardeners choose to leave the decorative seed heads standing for months, where they can provide architectural structure in borders. ‘Alliums are slightly different in that their seed heads often remain attractive long after flowering has finished,’ adds Mark Sage, horticultural expert at B&Q.
They can be left standing in borders or displays, where they can persist well into summer. They’re also brilliant for adding structural impact – particularly in cottage gardens.
2. Cut back once growth has died down
While allium flowerheads can be left standing, they can also be cut back after flowering – but it's important not to remove the foliage too early.
‘I always cut back the foliage once browned and leave the flower heads for as long as they look good, which can stretch well into the winter,’ says Nick Hamilton, owner of Barnsdale Gardens. ‘Once they start to disintegrate, I also then cut the flowering stems right back to the ground.’ This will prevent it from self-seeding.
Although the yellowing leaves can look untidy, resisting the urge to remove them too soon will reward you with stronger plants and healthier flowers next season.
3. Divide overcrowded clumps
Older alliums can sometimes become congested, which may affect flowering performance over time.
‘If you have clumps of older alliums that are becoming overcrowded, these can be lifted, divided, and replanted after the foliage and flowers have died down,’ says Richard. Dividing bulbs every few years can help rejuvenate plants and give you more alliums to spread around the garden.
Replant the divided bulbs in a sunny position with free-draining soil for the best results. Adding feed will also ensure they have the nutrients they need and replenished energy, as well as encouraging strong growth.
Follow House Beautiful on Instagram, TikTok and Pinterest
The Garden Edit
Folding Bistro Set, 3 Pieces
