growing sunflowers

How to Grow Sunflowers

Want to know how to grow sunflowers? This step-by-step guide will give you all the information you need to grow sunflowers from seed in your own garden or allotment.


About Sunflowers


Sunflowers are probably the biggest, tallest and cheeriest annual flower you can enjoy in the garden. They’re simple and fun to grow and make an excellent first flower for children. All you need is some space in the garden, in full sun (they need 8 hours of sun a day ideally), sheltered from winds – the flowers famously follow the course of the sun through the day.

sunflowers and sunflower oil


Discovered around 3,000BC, sunflowers were used by native Americans, the heads were harvested for oil and nutrient-rich seeds would be used as flour for bread. Today, both seeds and oil are still important foods, while the flowers make stunning additions to gardens. As cut flowers, they can be displayed in a vase and make a striking addition to any table or shelf!


For a competition winner try sunflower ‘American Giant’ which will reach 4m (13ft) or more in height; for something a little different try sunflower ‘Oranges and Lemons’ with blooms in shades of yellow and orange. Get the kids started with Little Growers sunflower ‘Sunshine Giant’, a selection specially selected for younger gardeners.


how to grow sunflowers

Clockwise from top-left: American Giant, Oranges and Lemons, Sunflower Little Growers sunflower Sunshine Giant



Sunflower varieties


Variety Approximate growing height Variety notes
American Giant 5m
  • A real giant among sunflowers
  • Strong stem requires no support
  • Great in borders and hedging
Toy Shop 90cm
  • Compact, bushy plants
  • A mix of single and double flowers
  • Great variety for cutting
King Kong F1 4m
  • Produces multiple blooms on each plant
  • Needs good support
Junior 60cm
  • Pollen-free variety with long flowering time
  • Multiple flowers on each branch
Giant single 4m
  • Quick growing
  • Single, tall flowers
Sunshine Giant 2m
  • Great variety for children
Jammie Dodger 1.2m
  • Perfect for garden display
  • Single, double and semi-double blooms
Solar Flash 40cm
  • Early flowering
  • Compact variety
Firecracker 60cm
  • Dwarf variety
  • Stunning red and gold flowers
Starburst Panache 1.8m
  • Unusual Catherine wheel appearance
  • Double golden blooms
Ginger Nut 1.5m
  • Bright orange flower with large heads
  • Blooms last up to 2 weeks after cutting



When to plant sunflowers 


When to Sow


For best results plant sunflower seeds from early March to mid-May, but always check the seed packet as some selections need more time to grow than others. To give them the best start, sow indoors as germinating seeds and young plants need some protection from frost. Alternatively, you can direct sow outdoors later in the season. They will usually flower from August and depending on selection, sunflowers take 80 – 120 days for plants to mature and develop seeds.


How to sow


Sowing sunflowers indoors

What you’ll need to get started:

  1. Fill the cells of your seed tray with John Innes Seed Sowing Compost or Gro-Sure Seed and Cutting compost leaving a 1cm gap below the top. Add one seed per cell and push it gently into the compost. Top up each cell with more compost and water well. Finally, add a plant label so you know what you’ve planted.
  2. Put the filled seed tray in a warm, bright spot; a sunny window sill or frost-free greenhouse is ideal for this. Your seeds should germinate in around two weeks.
  3. Once your seedlings have germinated and grown to around 5cm (2 inches), they can be moved into individual pots around 7.5cm (3 inches) in diameter. Add a small amount of multi-purpose compost to each pot then carefully remove the seedling from the tray and place it into the new pot. Fill with compost then gently push the compost down to compact it and secure the seedling. Water well and add your plant label. Position the pots in a warm, bright spot.
  4. Once your plants have reached 30cm (12 inches) in height, you can plant them in the garden or move them to a bigger pot. Don’t do this any earlier than May to avoid them being damaged by any late frosts.


Tip: be gentle when removing the seedlings from their cells to avoid causing damage to the plant or roots. If needed, gently run a narrow, flat object such as a dinner knife or even a plant label, around the inside of the cell to loosen it.

 from this point, you can start to use a liquid fertiliser to support the seedlings’ growth; the fertiliser should be diluted by 50% and used twice a week.


Sowing outdoors


  1. Before sowing, prepare the soil where you’ll be sowing your seeds; it should be a fine crumbly texture, weed-free and in full sun. Dig in organic matter such as Gro-Sure Farmyard Manure to ensure you grow the best plants. Do not sow seed outdoors until May; for a succession of blooms make repeated sowing over several months if you have space.
  2. Use an old cane to create a 12mm deep drill (a depression in the soil) and place seeds 10cm apart. Cover with soil and then give them water.
  3. Once the sunflowers become taller, use a cane to support the stems by loosely tying the stem to the cane with some string. This will help keep the stem strong and the plant will be encouraged to grow straight.


seedlings in pots


Next Steps


Sunflowers from indoor sowings


  1. Once seedlings reach around 5cm (2 inches), they can be pricked out into individual pots around 7.5cm (3 inches) across. Add peat-free, multipurpose compost to the bottom of each pot, then carefully transfer the seedling into the new pot. Be gentle to avoid causing damage to the plant; running a dinner knife around the inside of the cell will help loosen it and it will lift out more easily. Fill with compost then gently push the compost down to firm the seedling. Water well and add your plant label. Position pots in a warm, bright spot. For the best plants use liquid fertiliser diluted by 50 per cent and used twice a week.
  2. Harden plants off gradually by standing them outside on mild days, then bringing back inside to the warm at night. Do this for a couple of weeks.
  3. Once your plants are 30cm (12 inches) tall, plant in the garden or move to a bigger pot. Don’t do this before May or June to avoid them being damaged by late frosts. You will need to support plants with string tied to a cane until they establish. This will also encourage the stem to grow straight.


Sunflowers sown outdoors


  1. Once the seedlings germinate, thin them out so they are around 45cm (18 inches) apart – this will allow them to grow and develop well.
  2. Once sunflowers become taller, use a cane to support the stems by loosely tying the stem to the cane with string. This will also encourage the stem to grow straight.


Established plants


Give your growing plants plenty of water. Do not let them dry out, and continue with liquid feed now at full strength.


Pinching out sunflowers

Pinching out sunflowers will encourage plants to develop extra side stems and more flowers and is ideal if you are growing cut flowers. Pinching out the growing tip will stunt the plant so it produces more flowers. But, don’t do this if you want to grow a tall plant, perhaps for a competition!


  1. To pinch out, remove the growing tip of the plant using your thumb and forefinger, once the plant has reached around 25cm (10 inches) tall. Plants will still reach around 2m (6 ft 7in) tall but will produce four times the number of flowers.



How long do sunflowers take to grow?


There are various varieties of sunflowers, and each one will grow at a different rate. On average, though, it takes between 80 and 120 days for a plant to mature and develop seeds.




Deadheading can provide you with more flowers over a long season, while retaining the faded heads provides the birds with a treat and allows you to harvest seeds for sowing next year. If you are growing several plants, perhaps try both techniques.


Common problems, pests & diseases


The only problems are usually experienced at the seedling stage or shortly after planting out. Young plants are susceptible to attack from slugs and snails, so take precautions. Rough weather can also easily damage plants, so grow somewhere sheltered and stake plants if need be, especially tall ones.


Frequently Asked Questions



Will my sunflower come back next year? Sunflowers usually grown from seed are annuals which means they will not re-grow in spring unless you start them again from seed. There are perennial sunflowers but these are not usually as tall and have smaller flowers.


Which sunflower cultivar should I choose for the tallest possible plants Try sunflower ‘Giant Single’ which should reach 4m (13ft) or even higher!


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