How to grow sunflowers in your garden

A step-by-step guide to growing sunflowers from seedlings.

Sunflowers in field

by Ellen Kinsey |

Sunflower fields are a sign that summer has arrived, but they’re also very easy to grow at home. Sunflowers usually bloom from late summer to autumn, depending on the variety, and take up to 11-18 weeks to flower.

They’re very straightforward to grow from seed and can reach heights of up to 2-3 metres. In fact the tallest sunflower ever recorded was a massive 9 metres tall!

If you are looking to brighten up your garden or allotment with this sunny summer flower, then read on for everything you need to know about how to grow sunflowers.

What you’ll need:

· Sunflower seeds

· Seed tray or pots

· Multi-purpose compost

· Plant labels

· Waterproof marker pen or a pencil

Where to grow sunflowers

woman watering sunflowers

Sunflowers need lots of sun and grow best in fertile soil in a sheltered spot. They are great for planting in containers or pots, but if you’re looking to grow some really tall sunflowers, make sure to plant them in the ground.

When to plant sunflowers

You can sow sunflower seeds from April to May, individually in 10cm pots, or plant in the garden when the weather is guaranteed to be warm such as early June.

How to grow sunflowers

woman watering sunflowers

The best way to grow sunflowers is to find a sunny, sheltered spot in your garden or allotment. To make the soil suitable add lots of well-rotted manure or garden compost before planting. Water your sunflowers regularly. You may also need to add a stick to stake them if they’re in an exposed position.

There are different types of sunflowers so choose your variety carefully as some sunflowers will grow up to four metres tall (American Giant), while others can grow a lot smaller, such as ‘Teddy Bear’ (60-90 centimetres) or ‘Big Smile’ (30 centimetres).

How to plant sunflowers in pots

Step 1) Sow sunflower seeds into individual pots around 7.5cm in April. Push the seed 1.5cm into the compost top up with some water. Then cover the pots with a clear plastic bag and place them in a cool but bright place.

Step 2) After the sunflowers have germinated, ensure that they are well-watered until they’re ready to plant at the end of May.

Step 3) Prepare the soil by removing weeds and add plenty of organic matter. Plant the sunflowers at the same depth that they were in the pot.

Step 4) Make sure to water often and stake plants with a bamboo cane or similar to help their growth.

How to grow sunflowers in seed trays

Step 1) Start by filling the seed tray with some multi-purpose compost to around 1cm below the top. Then add one seed per cell and push it down into the soil. Fill each cell to the top with additional compost and top up with water. Then add a label to the seed tray so you can remember what plant it is.

Step 2) Position the filled seed tray in a warm, bright spot, either indoors on a sunny windowsill or outside in the garden.

Step 3) When your seedlings have germinated and grown to around 5cm (2 inches), you can move them 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 put it into the new pot. Fill up with compost then push the compost down to secure the seeds. Water and add your plant label.

Step 4) Once your sunflowers have reached 30cm (12 inches) in height, you can plant them in the garden or move them to a pot. Don’t do this any earlier than May to avoid them being damaged by any frost or cold conditions.

What are the growth stages for sunflowers?

• Planting the seedling

• Germination

• The leaf and plant develop

• Growing a bud

• Flowering

• Pollination

• Seed development

• Harvesting

Here is a chart by She Said Sunflower displaying the stages of growth.

She Said Sunflower sunflower growth
©She Said Sunflower

Tips for caring for sunflowers

Sunflowers in a basket

• Annual sunflowers need lots of water. A good idea is to feed them with tomato feed just before flowering. Don’t allow plants to dry out as tall varieties will not find it easy to recover.

• Very tall sunflowers may need the support of a garden cane, especially when growing in an exposed position.

• Sunflowers are generally easy flowers to tend to, but young seedlings are susceptible to damage from slugs and snails. If you are only growing a couple of sunflowers, be sure you allow them to grow quite tall before planting out. You could also use wildlife-friendly slug pellets or copper tape to discourage them from pestering the sunflower plant.

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