how to plant, grow & care for sunflowers
complete growing guide
There are three reasons for growing sunflowers from seed – instant architecture, great pollen source for bees and butterflies (as well as seeds for birds) and glamorous cut flowers. For all roles, you don’t want one or two sunflowers scattered here and there, like weird, out of place mobile phone masts, but sunflowers collected en masse in twenties or thirties as an abundant back door flower shop, or a patterned and sumptuous flowery screen. We sell a range of sunflower seeds as well as a few varieties as seedlings and jumbo seedlings to get you off to a flying start.
details
- Common name: Sunflowers
- Latin name: Helianthus annuus
- Type: Hardy Annual
- Height: Up to 3m (10ft)
- TLC rating: Easy
- Aspect: Full Sun, sheltered from winds
- Planting position: Mainly at the back of the border, unless they are smaller varieties
- Suitable for pots: Some smaller varieties, yes
- Good for pollinators: Yes
- Good for cut flowers: Yes
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how to grow sunflowers
where to grow sunflowers
Soil type: A good rich well drained soil, with added manure in the planting hole.
Aspect & position: The clue is in the name, sunflowers will want as much sun as possible, but a bit of shelter from wind too. Make sure you plant tall varieties at the back of the border as otherwise they will overshadow everything else.
when to plant sunflowers
You can start sowing sunflower seeds indoors in March, but it is best to wait until they are good sturdy plants, about 30cm tall, before planting outside in April or May. If you want to direct sow in the cutting garden, April should be fine if the soil is beginning to dry out.
how to plant sunflowers
sowing sunflower seeds
For statuesque sunflowers, sow them into a modular, divided seed tray full of multi-purpose compost in early March. When the seedlings are two inches tall, move them into 9cm pots.
Grow your seedlings inside until they reach about 30cm and then plant them out deep in the garden, adding a good barrow load of manure to the soil where they are to go. Don’t pinch them out, start tying them into the support as soon as you can.
planting sunflower seedlings
If you have grown your sunflowers from seed, or you have ordered our seedlings, we recommend potting these on into 9cm pots before planting in their final position outside.
Prepare a potting mixture using a good quality, multi-purpose, peat-free compost. Mix with a little horticultural grit to ensure good drainage. Fill a clean pot with the potting mix and make a hole in the centre, slightly deeper and wider than the plug. Position the plant in the pot, check the roots are fully covered and tap to settle the soil. Water well and leave somewhere bright but sheltered during the day. Cover with horticultural fleece overnight or bring indoors.
They will be ready to go into the garden once the roots have filled the pot. Our jumbo seedlings have larger root systems and can be planted straight into the garden if the weather is favourable. They will need plenty of elbow room when you plant them out, especially if you are growing bushier plants for cutting, so allow at least 45cm between plants. Enrich each hole with manure or well-rotted compost. Use a sturdy tree stake for each plant and tie in as you watch them grow.
how to care for sunflowers
watering
Once the plants are established in good, rich ground with sturdy support they will look after themselves and grow at an astonishing rate. Water them in dry weather as they are thirsty, particularly if you are growing them in pots. To get a really mammoth plant, or a good crop of cut flowers you will need to ensure that sunflowers get plenty of water.
fertilising
Ensure that you have given your sunflower plenty of food – well rotted manure or garden compost at the bottom of the planting hole is a must. You can also mulch the roots with more compost, and give the leaves a seaweed spray to give them a boost.
staking
A sunflower won’t stay upright without a bit of help. This is not the place for a tall, whippy bamboo. In a wind, they haven’t the strength to cope with the sunflower scale. Use a sturdy tree stake for each plant and make sure to tie them in as they grow.
harvesting sunflower seeds
As long as your sunflowers are not pollen free, they should produce edible seeds. Once the sunflower has finished flowering, you can cut the head off and let it dry out for a week or two in a warm, dry place. Once dry, rub the seed head and collect the seeds. You can either store the seeds until the spring when you can sow and grow more flowers, or you can eat the seeds as a tasty snack.
If you don’t need the seeds, you can also leave the seed head in place as a natural bird feeder for your garden birds.
growing sunflowers for cutting
If you want to pick your sunflowers as cut flowers, you will need to grow them in a different way to the statuesque single giants. Rather than wanting to maximise the sunflower’s height, you need to stunt the plants to make them easier to pick and increase the production of flowers.
To do this, pinch out the growing tips. When they reach about 20cm tall, (when they have 3 pairs of leaves) remove the tip between your thumb and forefinger. It feels brutal, but within a week you’ll see lots of buds breaking from the space between the remaining leaves and central stem. The sunflowers then grow to about 2m tall, and rather than producing one king flower to top the stem, and ten or fifteen sub flowers, you’ll quadruple the number of blooms, each one with a perfect long straight stem with one slightly smaller sunflower at its end. This is how I grow sunflowers in my cutting patch, sowing the seed straight in the ground.
My favourites to grow this way are 'ProCut Plum', with soft taupe and crimson flowers, ‘Red Sun’ with velvet flowers in the deepest crimson and ‘Valentine’ in a lovely pale lemon yellow. I sow two seeds spaced three inches apart with eighteen inches between that pair and the next. Sown like this I don’t waste any seed. If one germinates, I have the plants spaced at the right intervals. If both do, I dig one up and plant it somewhere else.
seasonal checklist
spring
- Sow seed indoors in March.
- Sow and plant outside in April and May
summer
- Tie plant in to stake as it grows.
- Harvest cut-and-come again varieties regularly.
autumn
- Allow giant varieties to dry in situ as natural bird feeders.
- Harvest the seeds, either to store or to eat.
winter
- Store collected seeds over the winter, ready to sow in spring.
pests, diseases & common issues
what is eating my sunflower leaves?
Young sunflower leaves are very attractive to slugs and snails, so check for slime trails and then search and destroy after dark. Once they are growing fast and furiously nothing is likely to faze them.
how do I control aphids on my sunflowers?
If you catch them early enough you can squash them and this attracts their natural predators to the feast – ladybirds and hoverflies. There is also an excellent safe spray – the SB Plant Invigorator that is very effective.
why are my sunflowers dying?
If they are still in a small pot, the most likely cause is over or underwatering. 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.
why are my sunflowers drooping?
Sunflowers can sulk for a while after being planted out until their roots have become established. If your mature plants are drooping that could be due to drought, so give them a drink and see if they pick up. In really hot weather the leaves will droop in order to conserve moisture but they should perk up as it cools down in the evening.
why are my sunflowers falling over?
Some varieties are very top heavy, so they need a sturdy stake to keep them upright.
why are my sunflowers so small?
Check what variety you have as there are a few smaller cultivars. Otherwise ensure that you have given it plenty of food – well rotted manure or garden compost at the bottom of the planting hole is a must. You can also mulch the roots with more compost, and give the leaves a seaweed spray to give them a boost.
my sunflowers don't have seeds
Some modern varieties are pollen free which makes them infertile. Alternatively, you might be short of pollinators in your area?
why are my sunflowers sticky?
This is usually an indication of aphids that secrete a sugary substance known as honey dew. It can result in a nasty sooty mould, so best to search out the aphids, squash them and hose off the honey dew. Also using SB Plant invigorator should prevent a build-up of these pests.
why is my sunflower not facing the sun?
Only young sunflowers turn to face the sun. Once the plant is mature it tends to stay put.
frequently asked questions
do sunflowers grow back?
The sunflowers that we sell are Helianthus annuus, so will not grow back next year. There are plenty of perennial varieties that you can try, alternatively, let your sunflower drop its seed and it will come back again as plenty of seedlings!
what do sunflowers represent?
Because of their cheerful and sunny disposition, most cultures associate sunflowers with good luck and happiness. Their amazing seed heads symbolise a bountiful harvest, as well as longevity and loyalty.
are sunflowers poisonous to cats or dogs?
No, all parts of the plant are edible, which means no problems for pets.
do sunflowers need a lot of water?
To get a really mammoth plant, or a good crop of cut flowers you will need to ensure that sunflowers get plenty of water.
can sunflowers grow inside?
They will survive, although they are unlikely to get enough sunshine to flower well indoors.
do sunflowers attract bees?
As long as they are not the pollen free varieties, yes, they do. On a sunny day, you will see bees getting drunk on the nectar.
do sunflowers close at night?
No, they do not.
are sunflowers hardy?
Yes, they are, but they are annuals which means that they die after they finish flowering.
can sunflowers grow in shade?
They can grow but are unlikely to flower well, if at all.
which sunflowers produce edible seeds?
As long as the flowers are not pollen free, they all produce edible seeds. Some varieties are grown specifically for their oil. Others are not as tall but grow huge heads of plump stripey seeds for snacking.
why are sunflowers so tall?
In order to seek out the sun, they need to be taller than anything else. Having originated in the North American prairies they need to outgrow all those grasses and monster prairie perennials.
what to grow with sunflowers
Tall sunflowers have rather ugly stout stems that you might want to conceal with the lovely glaucous foliage of globe artichokes. You can also try using them as planting poles for beans or squashes, although plant them some distance from the roots otherwise the competition for food and water will be fierce.
how to cut & arrange sunflowers
It is best to cut sunflowers first thing in the morning when they are still fully hydrated. Strip off the bottom leaves and plunge in a bucket of water before arranging in a tall heavy based vase or jug as they can be top heavy.
Get more inspiration for displaying your flowers with our flower arranging videos:
