Jun
19
2021

Growing sunflowers – a step-by-step guide

The Van Gogh iconic sunflower is arguably the most famous flower of the summer. His large, daisy-like face is a certified crowd puller and can beautify any garden.

Usually bright yellow, they also come in red, orange, or brown. While these colors don’t shine as brightly, they’re still bold enough to stand out from the rest of your garden foliage while adding a nice twist on the classic.

The other main characteristic of a sunflower is its height. The tallest varieties can reach over 16 feet, which is only a few feet less than the average height of a two-story home. It is therefore important that you consider where to place your sunflowers, as a cluster of tall sunflowers near your home can interfere with the natural light that comes in.

See: Garden ideas for borders – for a neat, tidy and decorative look

How to grow sunflowers

To help you grow your sunflower, we’ve put together a step-by-step growing guide, with expert advice on how to grow sunflower properly.

1. Pick your sunflower seeds

Photography / Mark Winwood

The real eye-catchers are the larger sunflower varieties. Aptly named, the sunflower varieties Skyscraper, Giant American, and Mammoth all fall into this category. These are all pretty standard in terms of what you would visually expect in a sunflower.

However, the smaller strains tend to deviate a bit from the script. The Firecracker, for example, only gets about 2-3 inches high and impresses with its mix of mahogany-red and amber-gold leaves.

Also note that Irish Eyes comes with the traditional golden leaves but has a green center instead of the usual brown.

2. Think of manure and compost

How to grow sunflowers

Photography / Anna Brockman

“Any fertile garden soil in full sun that is not soaked is suitable for sunflowers,” says Guy Barter, chief gardener at the Royal Horticultural Society.

” If in doubt, add 50g per square meter of general fertilizer before sowing or planting. Alternatively, you can add a bucket of compost or manure per square meter. ‘

3. Plant outside or inside

How to grow sunflowers

Photography / Anna Brockman

You can either sow directly outdoors or, if you decide to grow your sunflowers earlier in the season, start indoors. Sow your seeds about half an inch (1 cm) deep in a cell tray if you are growing indoors and just under 2 inches deep if you are growing outdoors.

Sunflowers started indoors will grow quickly due to the warm environment. You should see them start shooting within about a week. Take them outside when the frost threat is over or they might just start taking over your windowsill.

Barter recommends that you leave a space of about 30 cm between each plant and allow a 75 cm path for pruning where you have grown the plants in rows. The seeds will appear outside in about three weeks.

4. Caring for your sunflowers

How to grow sunflowers

Photography / Jason Ingram

Weeds and garden pests are your main enemies when caring for flowers. “Once the plants come out they will grow very quickly and to some extent shade the weeds, but some hoeing and hand weeding is required,” explains Barter.

‘Weeds that are allowed to overgrow the sunflowers spoil them very quickly.’ It is therefore important that you keep an eye on them regularly in case weeds show up.

Since sunflowers grow very quickly, pests are rarely an issue. A regular garden insecticide should do the job well if you are concerned. However, snails can be harmful until the first real leaves have formed.

“Either apply snail protection or grow plants indoors where snails can be excluded,” says Barter. “As soon as real leaves have formed, the plants are largely safe against mollusc pests.”

Since sunflowers are primarily a summer plant, they are very drought resistant when sown directly in the ground. However, the roots are less efficient for pot grown sunflowers and may need watering every 10 days during dry periods.

Finally, Marcus Eyles, Horticultural Director Dobbies garden center, recommends tying your sunflowers to a wooden stake to help them grow. This will help them grow straight and prevent a gust of wind blowing away your hard-earned sunflowers.

5. Cut your sunflowers

How to grow sunflowers

Photography / Joanna Kossak

If you decide to bring your sunflowers back to your home, you can always cut them up for display in a vase. “To cut off the flower stalks, because the flowers are just before the opening and only a few rays of the florets are visible,” advises Barter. “They also hold best when a flower protectant is added to the vase.”

Are sunflowers easy to grow?

Yes, sunflowers are easy to grow provided you protect the very young plants from pests. However, as soon as the first, tougher leaves have formed, the growing sunflower usually takes care of itself – it is heat-tolerant, fast-growing and quite resistant to pests.

Sunflowers are native to North America, so they grow happily in most states.

Can you grow sunflowers in pots?

Sunflowers can be grown in pots, especially the young plants. However, unless you have very large, deep pots for larger, ripe sunflowers, you’ll need to place them in flower borders as they will grow out of small containers quickly.

How long does it take for a sunflower to grow?

Sunflowers can reach up to 12 feet in just three months – expect ripe sunflowers within 70 to 100 days of planting.