How to grow sunflowers and add cheer to your garden 

We’ll tell you how to grow a sunflower at home, as well as look at how you can protect your plant from pests. My own efforts were gobbled up by snails and slugs last year, and I refuse to allow that to happen again. I am now armed with handy tips and tricks to stop your sunflowers from suffering the same fate. 

READ: When and how to grow courgettes – with tips from a National Trust kitchen gardener 

Sunflowers can be sown indoors in pots, or directly into the soil outdoors. The sowing season is usually between March and May, starting after the final frost, with seedlings appearing around 14-21 days after planting.  

It’s no surprise that sunflowers need sun to flourish. Lots of sun.  

“Sunflowers thrive in warm temperatures, so select a sunny spot in your garden that receives direct sunlight,” says Emma Fell of Hillier. 

“Before planting, it’s crucial to prepare the soil. Sunflowers prefer loamy soil [a mixture of sand, silt and clay] rich in organic matter, as they are very hungry plants. Remove any weeds, rocks or debris from the planting area. Loosen the soil to a depth of 15-20cm (6-8in) using a garden fork. Mix in compost or well-rotted manure to enrich the soil.” 

If you’re sowing your sunflower seeds in pots, make sure they’re kept on a warm, sunny windowsill to give them the best chance at germination. 

Not everyone has access to a garden. But this doesn’t mean you can’t attempt your own sunflower growing project at home.  

You might also, as is the case with me, be wary of sowing sunflower seeds directly outdoors. I have an army of snails and slugs waiting to demolish these tasty snacks in an instant. So far, no amount of eggshells or copper has impacted their appetite.  

The key to growing sunflowers successfully indoors is, much like outside, access to full sun. I have sown my seeds on south- and west-facing window sills that receive tons of sunlight and heat. (My cat also acts as a great barometer for knowing which window sill I should keep my pots on. Wherever he’s napping in the sun, that’s where you’ll want to keep your sunflower plants.) 

Fill individual pots with peat-free compost (ideally seed compost) and sow the seeds to the same depth as you would outside. Gardener David Domoney recommends sowing the seeds on their sides (though opinions on which direction to face the seed vary). Keep them somewhere sunny and warm, making sure the soil remains moist, until they’ve germinated. 

If you plan to eventually plant the sunflowers outside, Domoney says on his website: “When the seedlings have two sets of leaves, begin hardening them off. Take the pots outside on warm days and bring them back in at night. Continue this for a week to acclimatise the plants to outdoor conditions. Then plant them in prepared soil in the garden and water well.” 

There’s no reason you can’t have a stab at growing your sunflower indoors to see if it flowers. Making sure your indoor sunflowers receive enough sunlight is one of the most important factors, but so too is the size of the pot it’s growing in, and how much you water it.  

“If they are still in a small pot, the most likely cause [of sunflowers dying] is over- or under-watering,” writes gardener Sarah Raven. “Get them planted in the ground and they can find the water and food that they need, or a much larger container that will give them a good root run.” 

To reach its full flowering potential (and climb to its full stature) you might want to feed your sunflower. 

“Apply a balanced, slow-release fertiliser with a good source of nutrients, such as Phostrogen Organic All Purpose Plant Food, when the sunflowers reach a height of 15-20 cm (6-8in),” advises Fell. 

As you know by now, I’ve experienced first-hand the devastation slugs and snails can cause to young sunflowers. Thankfully, though, the risk reduces as the plants grow older and can fend for themselves. However you choose to keep slugs out of the garden, it’s one gardening job you’ll need to remain vigilant with once you know how to grow a sunflower. 

Aphids, on the other hand, can be a bit of an ongoing nuisance. If your sunflowers are sticky, it’s usually an indication of aphids, according to Raven, as they secrete ‘honey dew’.  

“This can result in a nasty, sooty mould,” she says. “So, it’s best to search out the aphids, squash them and hose off the honey dew.” 

Squashing aphids sounds cruel, but it’s a useful way to solve a wider problem on the plant. This is because squashing an aphid attracts their natural predators “to the feast”, according to Raven, which includes ladybirds and hoverflies. Once the predators are aware of the infestation, they should help to control the aphid population. 

Raven also recommends the SB Plant Invigorator spray, which she finds very effective at preventing the build-up of such pests.