|Official Plant Name||Helianthus Annuus|
|Plant Type||Annual Flower|
|Toxicity||Edible Petals & Seeds|
|Foliage||Broad, oval to heart-shaped, rough hairy leaves|
|Flowers||Huge flowers up to 30cm across with bright yellow petals|
|When To Sow||April, May|
|Flowering Months||June, July, August|
2.5 – 4M
0.5 – 1M
June – August
Preferred Soil Type
Most Soil Types
Moist but well drained
Neutral / Alkaline
Sunflowers are great for novices and experienced gardeners alike, and can find a place in many gardens.
In this guide, we’ll explore these flowers in a little more depth. We’ll take a look at the plant and learn a little more about it. Next, we’ll talk about why it might be a wonderful idea for you to grow some in your garden. After that, we’ll talk about where exactly they could be grown, and walk you step by step through sowing, growing and caring for your sunflowers.
Growing sunflowers is a great thing to do, whether just for their ornamental value, or for a range of reasons. Kids will love learning to grow them with you, and as an easy plant to grow, they can be your gateway to growing your own – no matter how green-fingered you may be. You might think you know these familiar flowers well – but they can be surprising. Read on to learn more.
What are Sunflowers?
The common sunflower, Helianthus annuus, is a tall and fast-growing annual. In summer, of course, the plant bears huge flowers up to 30cm across, with bright yellow petals and large brownish centres.
One fascinating thing about sunflowers is that they offer an example of a natural phenomenon known as heliotropism. While the flower heads are young, the flowers generally tend to turn to follow the sun across the sky as it travels from east to west. Researchers have come to the conclusion that sunflowers show this specific type of heliotropism because their stems elongate at different rates on each side at different times of day.
Scientists discovered that a sunflower head starts the day facing east. When the sun starts its progression across the sky, the east side of the stem grows more rapidly than the west side. Due to the unequal growth, the flower tends to bend in the direction of the sun. Then, when the sun sets, the growth favours the west side of the stem, so the stem bends east, and the flower head, therefore, leans back towards the east.
When the researchers tied the stem of the plant so they could not move, and the head faced away from the sun, plants had reduced foliage and lower biomass than those left undisturbed.
However, once mature, the sunflower behaves differently. As a sunflower’s developmental growth slows down, the sunflower’s circadian rhythm means that the plant reacts to sunlight with more vigour in the morning than it does later in the day. So a mature sunflower will tend not to move with the sun throughout the day, and will generally remain facing broadly east.
Facing the sun during the day in the early stages of growth brings benefits for the plants. Not only does it maximise photosynthesis, it also increases warming of the flower on each plant, thereby attracting more insects for pollination. East-facing mature sunflower blooms draw in five times the number of pollinating insects when compared to west-facing ones.
Why Grow Sunflowers?
Sunflowers are great plants to grow for a great many reasons. For one thing, they are a fantastic choice because they are very easy to grow. The seeds are large and easy to handle, and the plants grow quickly so you do not have to wait around too long to see impressive results.
Sunflowers look beautiful and very impressive, with their enormous heads. Planting just a few can have a big impact on the visual appeal in a garden.
Another thing to consider is that the structure of the sunflowers, which grow heads and shoulders above many other flowering plants, means that can add height and structure to a bed or border.
Sunflowers are great mixed in with other flowering plants in an ornamental border. But they can also work well as companion plants in a kitchen garden. Not only do these flowers attract plenty of pollinators to your garden while they are in bloom, they also attract predatory insects like lacewings and parasitic wasps that help keep pest numbers down.
They can also serve as structure for climbing edibles like beans to grow up. It is also worth noting that they are an edible plant in their own right. They not only produce edible seeds towards the end of the season – the petals are edible too.
(One thing to note, however, is that sunflowers can suppress the growth of certain other plants when grown close by. You should avoid planting sunflowers too close to potatoes, for example.)
Sunflowers also provide a range of other yields, from organic matter for green manures and composting, to dyes, and fibres. And the pith inside the stems which is one of the lightest substances known to science. It is used in making life-saving equipment and slides for microscopes, for example.
Where to Grow Sunflowers
As mentioned above, sunflowers could be grown in an ornamental bed or border, or in a vegetable garden. They will do best, as their name suggests, in an area that receives full sun. Though they can also potentially cope with partial shade, they do best where they receive at least 6-8 hours of direct sunlight per day.
When choosing a location for growing sunflowers, it is important to understand that they have long tap roots (to anchor them well as they grow so tall). They need to be planted in an area where the soil is deep enough to accommodate the root system. And they will do best where that soil is loose, moist and well-draining. Avoid areas with compacted soil, and areas with soils that are outside of the 6.0-7.5 pH range. The soil should be fertile and nutrient-rich, and it is a good idea to top-dress the area with plenty of organic matter before planting.
In order to avoid pest issues, it is generally best to sow seeds indoors before transplanting seedlings later to their final growing positions. Seeds should be sown in small pots, modules or soil blocks indoors before the last frost, or, if you do prefer to dow directly, this should be done after you are certain that the last frost of the winter has passed. Ideally, you should wait until the soil has warmed to between 13 and 16 degrees.
Choose a fertile and balanced, moist yet free-draining growing medium for sowing your seeds. Sow each seed by making a hole in the growing medium and placing a seed in each one, at a depth of around 2cm. Gently firm the soil back over the seed and water it in. Then leave it in a sunny spot for germination to take place. If you wish, you can improve your chances of success by sowing 2-3 seeds in each pot, and then removing the weaker seedlings once they emerge to leave one seedling per pot.
One fun (and educational) game for kids is to have each child plant a sunflower, then have a ‘race’ to see whose grows the tallest the fastest. Each child should take care of their own seedling, watering it as required and perhaps even talking or singing to it so experiment and see what has an affect on its growth.
Caring for Sunflowers
Sunflowers to not require much care. They do not need much fertilizer and, in fact, will not thrive if you fertilise them too much. Coddled plants will tend to have weaker stems, that can break towards the end of the summer or in autumn.
The main things you will have to think about are:
When the seedlings are still small, especially if they are growing in a heated indoor space, you will have to regularly water to make sure that the growing medium around the root zone of your plants does not dry out.
However, once the plants are more established, and certainly after you have hardened them off and transplanted them to their final growing positions, you should water far less frequently. Watering well on a less frequent basis rather than watering little and often is the best policy. It will encourage the plants to root deeply, which will make them stronger as the season progresses.
The biggest problems for sunflowers are often slugs and snails. They love sunflowers and can quickly destroy a young plant. Never use slug bait/ slug pellets in an organic garden. Instead, try to take natural measures to reduce slug and snail populations in your garden – such as attracting plenty of birds, amphibians and mammals that eat them. Choosing the right plants and creating different habitats (garden ponds and wild native hedgerows for example) should help. You can also place collars or barriers of material around young sunflower plants, and/or place slug traps nearby.
Another thing you might notice about sunflowers is that ants may herb aphids onto them. One of the strange phenomena that occur in a garden is ants ‘farming’ aphids. But if ants herb aphids onto sunflowers, it is worthwhile remembering that this means they are keeping them away from your fruits and vegetables. So sunflowers could also serve as a useful companion plant in a kitchen garden because they can serve as a trap crop.
Finally, it is likely that you will need to provide tall sunflowers with some support. There are a number of methods you could use to support your plants, but the simplest idea is just to insert a bamboo cane or long stake or branch into the soil and to tie the sunflower gently to that support as it grows. Remember not to tie it too tightly, so it can grow freely and face the sun as it needs to do.
You can harvest sunflowers while they are in full bloom and use them for displays of cut flowers inside your home. Ideally, cut the stems early in the morning so they will last longer. You can also dry them for longer-lasting displays.
If you want the seeds, leave the sunflowers in place into autumn for these to form, and, if you want to stop birds from eating them all, keep a close eye on the heads, so you can get to them before they are gone. You can obviously eat some seeds. But why not also save some to sow in your garden next year?
A permaculture garden designer, sustainability consultant and freelance writer, Elizabeth works as an advocate for positive change. She aims to inspire others to reconnect with nature and live in a more eco-friendly way. She also tries to practice what she preaches as she tends her own forest garden, polyculture beds and polytunnel. See her personal website here.