Image credit: Shutterstock / Alex Manders
Are the impressive pom-pom blooms of your ornamental allium plants past their best? Before you reach for the secateurs at the first sight of frazzled petals, it’s useful to know what to do with alliums after they finish flowering.
When daffodils finish flowering, for example, it’s better to leave them be for a while so that the bulb below ground can get enough nutrients to survive the winter and return triumphant next year. But not all bulbs are the same.
Alliums are a hero plant for beginner and expert gardeners alike. They’re one of the best low-maintenance garden flowers for your patch – rewarding minimal effort with generous plumage. In fact, alliums are so easy-going that it’s really up to you if you want to cut the flowers back or not.
We spoke to gardening experts to explain what to do with alliums after they finish flowering, so you can make the best decision based on your garden’s needs.
Alliums aren’t like most bulbs, according to Monty Don
Some people can’t bear the sight of crispy, withering leaves and petals. Those keen to clear any raised beds of spent flowers, including alliums, will be pleased to hear that they can wield their scissors in confidence.
“Unlike most bulbs, the foliage of alliums can be cut back immediately after flowering,” writes Monty Don. “In a border this will create space for planting tender annuals such as cosmos, zinnias, tithonia or sunflowers.”
Small garden owners may want to switch up flower displays as much as possible – in which case you can cut alliums back. Though it’s best to give the bulb some time to absorb nutrients through its faltering leaves.
“If you’re keen to tidy alliums up more immediately, wait for the foliage to shrivel and turn yellow, then snip the stem at the base with clean, sharp secateurs,” says Sarah Veniard, garden designer and founder of Discovering Gardens.
“It’s important to be patient and wait for the foliage to die back as, even after flowering, the leaves are still photosynthesising and sending valuable energy into the bulb. This will allow the bulb to over-winter successfully and provide you with a magnificent display again the following year.”
Writing for the Daily Mail’s Weekend Magazine, Monty Don explains that allium leaves can often look like they’re starting to die even before flowering. It’s important not to mistake this as a dud plant and cut it back, as it’s just a quirk affecting many alliums.
“The leaves, which fold halfway up and droop in an idiosyncratic manner, have a tendency to start to die back at the tips before they come into flower,” he says. “This is not due to any illness or problem; it is simply a common feature of early alliums that the foliage dies back before the flowers fully open.”
It’s also a good idea to mark where you’ve planted the allium bulbs, so that you don’t damage them with future planting projects.
“Just let them do their thing”
Even though alliums are tremendously hardy perennials, not touching them after flowering is the best way to ensure they return in the best health.
“Just let spent alliums do their thing, Guy Barter, chief horticulturist at the Royal Horticultural Society, tells us. “The leaves die back to nourish the bulb and the seedheads dry out gradually to look very architectural, particularly when frosted.”
Veniard agrees that alliums can be valuable in the bleaker winter months. “If left in the garden, the spent flower heads will continue to provide their gorgeous sculptural form to your borders into winter, providing interest when your other plants may be going dormant,” she says.
“Don’t water spent plants and leave potted ones to get a good bake but not become totally desiccated,” Barter adds. He notes that autumn rain and winds will cause some alliums to collapse. “Consign them to the compost bin," is his advice.
Feed the birds and fill your vases
Calling all flower arrangers: dried alliums are a wonderful addition to a vase. “You can cut the seedheads and dry them inside,” says Veniard. “They make a fantastic decoration in a vase; particularly beautiful when accompanied by the soft, wispy stems of dried grasses.”
Barter agrees that the dried seedheads look good as indoor arrangements. “You can cut the flowers in bloom and dry them indoors,” he adds. “Some colour is often retained, but it seems a waste."
Leaving the seedheads to dry on the flower in the garden has another use. Birds will enjoy snacking on the dried seeds. You can also collect the seeds yourself to grow more alliums from scratch yourself.
“But given the low price of bulbs and the time and space needed to raise plants to flowering size [often a couple of years], few gardeners bother,” explains Barter.
Interested in planting alliums and other low-maintenance flowers in your garden but not sure where to start? Sarah Veniard is a garden designer and founder of Discovering Gardens. Bookings are open for her Planting Advice Consultations and her Garden Design Starter Pack for beginners. You can find her on Instagram @discovering_gardens or contact her via her website.
Our expert pruning and watering hacks include a top tip to keep them flowering from Alan Titchmarsh.
Don’t make these bird-feeding mistakes. Expert advice on how to feed birds in your garden safely.
Blighted by buzzing? How to keep wasps out of your garden without harming them so you can enjoy the summer.
The ways you could be breaking the law in your back garden - with expert advice on how to avoid neighbour disputes, a fine or even a prosecution.
Everything you need to know about Japanese knotweed, the fast-growing plant nobody wants in their garden.
