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.
Discovered around 3,000BC, sunflowers were used by native Americans, the heads harvested for oil and nutrient-rich seeds which 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.
Clockwise from top-left: American Giant, Oranges and Lemons, Sunflower Little Growers sunflower Sunshine Giant
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:
- Sunflower seeds
- Cell seed trays
- John Innes Seed Sowing Compost or Gro-Sure Seed and Cutting compost
- Plant labels
- Waterproof marker pen or a pencil
- 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.
- 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.
Sowing outdoors
- 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.
- 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 a water.
Next Steps
Sunflowers from indoor sowings
- 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.
- 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.
- 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
- Once the seedlings germinate, thin them out so they are around 45cm (18 inches) apart – this will allow them to grow and develop well.
- 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 will encourage plants to develop extra side stems and more flowers and is ideal if you are growing for cut flowers. But don’t this if you want to grow a really tall plant, perhaps for a competition!
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.
Deadheading
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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