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.
Written by: Sarah Raven
Last updated: 8th Jan 2021
A good rich well drained soil, with added manure in the planting hole.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Some varieties are very top heavy, so they need a sturdy stake to keep them upright.
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.
Some modern varieties are pollen free which makes them infertile. Alternatively, you might be short of pollinators in your area?
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.
Only young sunflowers turn to face the sun. Once the plant is mature it tends to stay put.
Frequently asked questions
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!
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.
No, all parts of the plant are edible, which means no problems for pets.
To get a really mammoth plant, or a good crop of cut flowers you will need to ensure that sunflowers get plenty of water.
They will survive, although they are unlikely to get enough sunshine to flower well indoors.
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.
No, they do not.
Yes, they are, but they are annuals which means that they die after they finish flowering.
They can grow but are unlikely to flower well, if at all.
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.
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.
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.
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.
