Top tips for growing giant sunflowers

Birds love to feed on the seeds of sunflowers in the autumn
Image: Sunflower 'Russian Giant' (Start-A-Garden™ Range) from Thompson & Morgan

Sunflower seeds are easy to sow and grow, and a great way to get children interested in gardening. With the right care and attention, your sunflowers can reach impressive heights. We talked to Richard Hope, recent winner of Thompson & Morgan’s Tallest Sunflower Competition, to learn the secret of his success. Here are his top tips for growing the tallest, award-winning, giant sunflowers:

• Growing competition-sized sunflowers takes complete dedication from beginning to end. If something needs doing and you put it off, you could destroy your plants.
• Nice, warm temperatures over the summer and into early autumn will help, but remember to give plants protection against extreme weather.
• It’s best to grow your sunflowers against a solid, south-facing wall. You’ll need to prop a ladder against it to climb up and support your plants.
• I always use the seed from my previous year’s biggest sunflower.
• This year I had the best sunflowers I’ve ever grown and the only thing I did differently is use incredicompost® with incredibloom®
• I start my plants off in the greenhouse and re-pot them into bigger pots until there’s no further chance of frost. Then I plant them outside.
• It’s really important to protect your sunflowers from slugs as they can decimate your plants in the early stages.
• Until my plants are about 10ft (3m) tall, I feed them with high nitrogen feed. Then I ease off as the incredicompost® and incredibloom® give the plants enough.

Best giant sunflower varieties to grow from seed

Sunflower ‘Russian Giant’ reaches heights of about 3m
Image: Sunflower 'Russian Giant' from Thompson & Morgan

When you think of sunflowers, the first image that comes to mind is likely to be a large, bright yellow bloom with a brown heart. But they’re also available in a wide range of colours including red, orange, green and white. Whether you want to grow annuals or perennials, compact varieties or tall giants, there’s a surprisingly large number of sunflowers from which to choose. 

If you’re hoping to grow giant varieties that will take the cup at the village show, one of the tallest sunflowers is ‘High Hopes’. At 4.5m high, it towers over all other flowers in the garden from July to October. 

Another popular choice, ‘Russian Giant’ is an easy option to grow with kids. Reaching 3m tall and with blooms spanning 30cm across, it’s especially easy to collect the edible seeds. Children will love toasting the seed kernels for a healthy snack and birds always appreciate any leftovers when the flowers fade.

Slightly less tall, but still long-stemmed, sunflower ‘Astra Gold’ is a good choice for the back of your border. Featuring unusual gold ruffled petals, it’s lovely as a cut flower too.

And for even more height and stature in the back of your border, ‘Solar Eclipse’ has pure yellow petals flanked with a rich red flame, creating a spectacular ring of fire effect. 

How to grow sunflowers from seed - video tutorial

Sunflowers are the perfect flower to get children involved and interested in gardening. Watch our quick video tutorial to see just how easy it is to grow sunflowers in pots or borders. Birds also love the seeds, so you’ll be doing your bit for wildlife by growing a few in your garden!

For more information and sunflower growing advice, visit our dedicated hub page which covers everything you need to know about growing these special blooms. And if you're looking for helpful tips on growing fruit, vegetables and flowers with children, browse our Kids Grow section.