From Van Gogh’s iconic paintings to towering summer displays, sunflowers have become the ultimate symbol of the season. But when the petals start to drop, don’t rush to cut them down.
If you’re wondering what to do with sunflowers after flowering, the weeks that follow can be just as useful, whether you're hoping for more flowers, saving seeds for next year or feeding garden birds
What you do next depends on the type of sunflower you’re growing and what you want from it, from a wildlife-friendly garden to a future crop of seeds.
Should you deadhead sunflowers after flowering?
Not always. Branching or multi-flowered sunflowers produce several flower heads on side stems. Remove each faded bloom as it finishes flowering to redirect the plant's energy into producing more flowers over the coming weeks. Once all the blooms have finished, you can cut the plant back.
Single-stem varieties are different. Grown for one large central flower, they shouldn't be deadheaded until the flower head has fully developed. The RHS also recommends leaving sunflower heads you want to collect seed from, or those you're growing to provide food for birds, rather than deadheading them.
"Deadheading sunflowers is an important task, as by doing this, you can stop the production of seeds, and shift the plants' focus back to growing new flowers," says David Denyer, florist and gardening expert at eFlorist.
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Liam Cleary, garden retail director at Old Railway Line Garden Centre, warns against rushing to tidy them up.
"I always tell people to leave the flower head alone for a while. As the yellow petals begin to fall the back of the flower changes from green to a yellow-brown colour, the seeds are still developing. If you cut the stem too soon, these seeds won't fully develop."
Leave sunflower heads for birds
Fading sunflower heads can become a valuable food source for wildlife, turning spent blooms into a simple way to support garden birds. "If you want to support birds, simply leave the heads standing on the stem. This is one of the best things you can do for wildlife," says Dariia Plaksina, a botanist at Botan App. "Many birds will visit sunflowers from September. I've watched goldfinches work through a head in under an hour."
Tammy follows the same approach when she doesn't need the seeds. "I often leave the seed-heads standing in the garden, if I have no use for the seeds, because the goldfinches and other birds will feed on them throughout the late summer and autumn."
If birds begin eating the seeds before you're ready to collect them, Liam recommends loosely covering the head with fleece, muslin or a paper bag whilst it finishes ripening.
Save sunflower seeds for next year
To save sunflower seeds for sowing, leave the flower head on the plant until the seeds are plump and firm and the back of the head has changed from green towards yellow or brown.
Tammy says the head is ready when "the back of the flower head has turned yellow to brown, flower petals have withered and fallen off, and the seeds are plump, with firm striped shells that can be rubbed free with the thumb".
The seeds should feel hard and come away with gentle pressure. If they are still soft or firmly attached to the flower head, leave them for a little longer.
Wet weather and hungry birds can spoil the crop before it is ready, so cut the head with part of the stem attached and allow it to finish drying somewhere sheltered if necessary.
How to dry and store sunflower seeds
Once the seeds are ready, cut the stem below the flower head and move it to a dry, well-ventilated space. Dariia suggests leaving around 30cm of stem attached so the head's easier to hang upside down.
"Hang the head upside down in a dry space. I put a paper bag loosely over the head secured with an elastic band. Do not use plastic bags! They trap moisture and cause mould."
Once the seeds rub free, spread them out in a single layer and allow them to dry for a week or two in somewhere warm, dry and well-ventilated. Liam recommends storing completely dry seeds "in a paper envelope in a cool, dry place," then labelling the envelope with the variety and year before keeping it somewhere cool, dry and dark until spring.
Common mistakes to avoid
"The biggest mistake made is to cut the flower heads off too early while the seed is still green or to store the seed before it is completely dry, which can cause it to mould and fail to germinate the following year," says Tammy.
Once the seeds are completely dry, store them in a paper envelope rather than a plastic bag or sealed container, where trapped moisture can lead to mould.
Whether you leave your sunflower heads standing for wildlife or save the seeds for next year's garden, a little patience helps these cheerful blooms keep giving long after flowering.
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