Lars Lund

24 May 2023 11:30

Sunflower cultivation: Sun even in cloudy weather


It is the kids favourite flower, the pride of the allotment, the competitor’s favourite ornamental plant, and the blackbird’s afternoon snack. 

The sunflower is beloved by many and fortunately easy to grow. The sunflower belongs to the asteraceae and can have a flowerhead from 5 cm and up to 30 cm. It has the colours of the sun, which can vary from bright yellow to red, or almost as black as a solar eclipse. The yellow colour is the most common. 

The insects are lured in by the smell and colour. The darker centre of the flower is actually seen more clearly by many insects, than for example the yellow colour. In the industry, the seeds are for example used for oil production and bread.

The sunflower is most commonly known as an annual plant, which grows and grows, and can become several meters high. When autumn arrives, the sunflower wilts and releases its seeds, which are gathered like a little package. It is possible to find naturally sown sunflowers the following year. However, the birds often eat all the seeds during winter.


A perennial as well

There are also sunflowers, which are herbaceous perennials. Here are a few examples:  

The Helianthus de Capetalus ‘Soleil d’or’ is a sunflower with arrow shaped leaves with a very unique and beautiful flower. It is also grown because of its beautiful green leaves, because it takes a little extra heat to get it to produce flowers.

This is a little easier with the Helianthus Maximillian sunflower, which has yellow flowers all the way up the stem. Its flowers last long, also as cut flowers.

Another popular sunflower is the ‘Lemon Queen’. The colour is light yellow, and the flower is about 6 cm. Nevertheless, it is quite beautiful and forms a close stem, that makes it look like a bush, which can become approx. 2 m high. It is also suitable as cut flower.

The perennials spread from the centre of the plant out to all sides with strong, creeping rhizomes. If the soil is very fertile, it might spread more than you wish and take up a lot of space. It should therefore be planted where there are no other herbaceous perennials.


Success with annuals

If you buy annuals, there is no risk. They can be planted by a path, in front of the house, by the kid’s playground, in pots and containers. There are a lot of different varieties in many colours and sizes. If you like to break records, the sort ‘Skyscraper’ might be for you. It is known to easily become 4m high. If you like short plants with huge flower heads, the sort ‘Sunspot’ might be for you. There are also sunflowers that resembles giant dahlias, like the sort ‘Teddy Bear’.


How to get more sun

You can sow sunflowers directly into the ground, but you get the most out of them, if you pre-germinate the seeds in a pot indoors.


Use a suitable pot or seed tray with potting soil. Here you can start in mid-April. Sow 2-3 seeds 2-3cm deep and keep the soil moist until the seeds have sprouted. When the seeds have sprouted, you can repot them to make sure there is only one plant in each pot. The small seedlings should be separated to make sure each plant has its own space and pot to grow in. If it is warm, you can move them into the greenhouse. Before they are planted out, they must be hardened off slowly. For a week, put the plants outside for a few hours, each day a bit longer. When they have gone through this process, you can plant them out from mid-May, but preferably wait until June.

Direct sowing

Sunflowers need warmth and sun. Find a warm spot outside with as much access to sunlight as possible. If you want the flowers to grow in rows, make a furrow a couple of centimetres deep. Then sow the seeds with a distance of about 10cm. Lightly press the soil over the seeds. Water and make sure to keep the soil lightly moist.


Sunflowers need plenty of water and should get a little fertilizer a couple of times during the summer. They are usually quite resistant towards wind and can stand without plant support because of their strong roots and stem. When the flowers begin to wilt, you can harvest the seeds, but let them mature on the plant for as long as possible. Choose seeds from the largest flower heads. You can easily remove the seeds by bending the flower head a couple of times to loosen the seeds.

Search for pictures online

Search for sunflower varieties online, and you will find a varied selection of both annuals and perennials. At the same time, you get a sense of the different colours and heights, so you can choose the varieties that fits best to your wishes.

Did you know…

…that the record for the highest sunflower is 9.17 m? The record holder is Hans-Peter Schiffer from Germany. In Denmark, the record is 4.85 m.

…that sunflowers turn their heads towards the sun and at night they move their heads back towards the morning sun? Sunflowers have a built-in biological clock, that tells them every night, that it is time to turn the heads towards east. The biological clock stops when the plant stops growing. At that point, all sunflowers face east. That is supposed to provide optimal pollination from insects. The clock is depended on the rhythm of nature. If you for example place the sunflower under artificial light for 30 hours, their biological clock will stop as well.

…that you can have a lot of beautiful sunflowers all summer long with the sunflower bush Helianthis SunBelievable ‘Brown Eyed Girl’? It first came on the market in 2018, where it was presented at the famous Chelsea Flower Show and won 3. place as the newcomer of the year. The sunflower is not especially high, but it constantly develops new flowers. One single bush can produce 1000 flowers from June till November. It is quite remarkable.

Om Lars Lund

Lars Lund
Danish horticulturist and journalist
Lars Lund has for many years engaged in the garden and greenhouse. Lars has published many books about greenhouses, and he has participated in many Danish horticultural TV shows. He is a walking garden encyclopaedia, and he has answers for most basic cultivation questions – also the more ambitious ones.  

Get to know Lars Lund