How to grow sunflowers

Sunflowers are easy to grow from seed and are ideal for growing with children. They bear impressive, long-lasting flowers, and look fantastic in gardens and allotments. They also make an excellent cut flower. They are non-toxic to pets and humans.

Perennial sunflowers come back year after year but annual types flower, set seed and die in one year.

Did you know? Sunflowers are related to Jerusalem artichokes, Helianthus tuberosus. If you plant Jerusalem artichokes they will bear beautiful, sunflower-like blooms, provided conditions are hot enough and they receive enough sunshine.

Jump to

• Where to grow sunflowers
• When to plant sunflower seeds
• How to plant sunflowers
• Growing sunflowers in pots
• Caring for sunflowers
• How to harvest sunflower seeds
• How to propagate sunflowers
• Pests and diseases
• Sunflowers to grow

How to grow sunflowers

Growing sunflowers from seed is easy – you just need a sunny, sheltered spot and good soil – add some well-rotted manure or garden compost before planting to enrich your soil, if necessary. Protect the young plants from slugs and snails, and water regularly. You may also need to stake them if they're in an exposed position.

Choose your variety carefully as dwarf sunflowers grow to around 50cm, while taller varieties can reach up to 3m in height. Sow seeds in pots from April and plant out a few weeks later. Water frequently and, if growing for height, feed weekly with a nitrogen-rich fertiliser to encourage them to grow tall. You may need to stake some of the taller varieties.

Where to grow sunflowers

Sunflowers need sun. For best results, grow them in rich, fertile soil in a sheltered, sunny spot.

Sunflowers grow well in pots but if you're growing for height, it's best to grow them in the ground.

When to plant sunflower seeds

The best time to plant sunflower seeds is between April and May. You can sow sunflower seed as late as mid-June but bear in mind they take up to 18 weeks to flower from seed so they may not flower before autumn.

Sow seeds individually in 10cm pots of peat-free, multi-purpose compost. Cover the pots with a clear plastic bag and place them in a warm spot for the best chances of germination. Remove the plastic cover once the seedlings have emerged. When the seedlings are large enough to handle, harden them off gradually – for about two to three weeks – then plant them outdoors. You may need to protect them from slugs and snails. Alternatively, just sow the seeds direct in the ground from mid-April onwards, but be mindful of slugs and snails.

How to plant sunflowers

If your garden has a lot of slugs and snails, your sunflowers may benefit from being potted on into larger pots of fresh compost, then hardened off before planting out into the soil. This means the plants will be bigger when in their final growing positions, and therefore more resilient to slugs and snails. Regardless of how big they are, don't plant seedlings out until the soil has warmed considerably and the risk of frost has passed.

Watch Monty Don sow sunflower seeds as part of his giant sunflower trial, in this clip from Gardeners' World:

When planting out, prepare the soil by removing weeds and if necessary add plenty of organic matter such as compost or well-rotted manure. Plant the sunflowers at the same depth they were in the pot. Water well and stake taller varieties with a bamboo cane or similar.

Here, Monty plants out his sunflowers and explains how to stake them:

Growing sunflowers in pots

Sunflowers do well in pots, although they usually don't grow as tall as those growing in the ground. Sunflower plants are heavy feeders, so make sure you water the pots regularly (daily in hot weather) and feed fortnightly with a nitrogen-rich fertiliser, switching to a high-potash fertiliser, such as a tomato feed, when the plants begin to bloom.

To grow sunflowers in containers, sow the seeds in small pots as you would normally in spring, and then transplant them individually into larger ones when they're large enough to handle, eventually potting them on into a 30cm pot of loam-based, peat-free compost, ideally with added organic matter. Stake taller varieties as you would for plants growing in the ground.

Caring for sunflowers

Annual sunflowers need plenty of water and will suffer if allowed to dry out. If you're growing for height, feed them fortnightly with a nitrogen-rich fertiliser and then switch to a potash-rich tomato feed just before flowering.

Stake tall varieties with a sturdy cane to prevent wind rock, especially if growing in an exposed position.

After flowering, you can deadhead spent blooms or leave the faded flowerhead intact so the birds can feast on the seeds. Once they have eaten their fill pull out the entire plant and put it on the compost heap, chopping up the thick stem so it will rot down more quickly.

Find out which sunflower fares best in Monty's giant sunflower trial update:

How to harvest sunflower seeds

After flowering, sunflower heads develop masses of seed. You can harvest these to use in cooking, but bear in mind you will need to remove the tough seed coat before eating. Better still, remove the seeds from the seedhead and leave them to dry for a few days, before storing in a paper envelope in a dry spot, so you can sow them the following year. Make sure you leave some seeds for the birds, too.

How to propagate sunflowers

After harvesting the sunflower seeds, space them out on kitchen roll to dry for a few days, and then store in a paper envelope in a cool, dry spot for winter. Sow the seed in 7cm pots of peat-free, multi-purpose compost from April the following year.

Pests and diseases

Sunflowers are generally trouble free, but young seedlings are susceptible to slug and snail damage. If your garden has a lot of slugs and snails, avoid planting sunflowers until they are big enough to withstand being attacked. If growing sunflowers in a greenhouse or cold frame, then regularly inspecting and removing slugs and snails can be effective. Also consider using wildlife-friendly copper tape to keep molluscs at bay.

Black spots on sunflower leaves are most likely caused by sooty mould. Sooty mould forms on honeydew, a sugary substance excreted by sap-sucking insects like aphids and mealybugs. If you're also noticing a lot of ants on your sunflowers, this is because ants 'farm' aphids for their honeydew, which they drink. As your sunflower grows it becomes less attractive to aphids – they prefer young foliage – and so there will be less honeydew and less sooty mould. However, if you're worried, you could rub the aphids off your plants with your fingers.

Sunflowers to grow

Sunflower ‘Russian Giant’

'Russian Giant' is a huge annual sunflower, bearing a single flower and growing as high as 3m. This traditional yellow-flowered variety blooms from July to September.

Height x Spread: 3m x 60cm

• Buy sunflower 'Russian Giant' from Thompson & Morgan

Sunflower 'Shock-o-lat' F1

This red-flowered 'Shock-o-lat' bears large flowerheads with bronze-red petals with yellow tips and a red-brown central boss that yields edible seeds. The stems have a purple tinge, which contrasts well with the green of the leaves.

Hx S: 2m x 60cm

• Buy sunflower 'Shock-o-lat' from Dobies

Helianthus ‘Lemon Queen’

This perennial 'Lemon Queen' bears masses of small, lemon-yellow blooms from July to September, and comes back year after year.

H x S: 2m x 45cm

• Buy sunflower 'Lemon Queen' from Crocus

Sunflower 'Choco Sun'

One of the best dwarf sunflowers to grow, 'Choco Sun' is fast growing and bears masses of large yellow flowerheads. It's a perfect sunflower for pots and fun for children to grow.

H x S: 35cm x 35cm

• Buy sunflower 'Choco Sun' from Thompson & Morgan

Frequently asked questions

When do sunflowers bloom?

Sunflowers bloom from summer into autumn, typically around July to September. The flowering time can depend on several factors, including when you sowed the seed, weather conditions, and availability of food and water.

Are sunflowers perennial?

Sunflowers can be annual or perennial. The tall, often single-stemmed varieties we grow in our gardens tend to be annual sunflowers, while perennial sunflowers are known by their botanical name Helianthus, and include the lovely variety 'Lemon Queen'.

One of my sunflowers has multiple heads growing all up the stem. Is this normal?

This is perfectly normal, and usually welcomed, as it means more sunflowers from one plant. Some sunflowers are multi-branching, which means they produce lots of flowers all along the stem.

Why are the bottom leaves of my sunflower seedlings turning yellow?

Seed leaves are the first leaves that emerge from the seed as it germinates. These are not 'true leaves' and so die back once the true leaves have started growing and photosynthesizing. This is nothing to worry about.