Sunflower

The sunflower’s American origin

Native populations in North America originally grew the sunflower for its edible seeds, its oil and as a source of dye. In the 16^th century, it was introduced into Europe, where it was first used as an ornamental plant. From the 18^th century, the sunflower was grown in Russia for its oil, as it was the only fat allowed by the Orthodox Church during Lent. In the 19^th century, its cultivation as an oilseed crop extended across the whole of Europe. Nowadays, the sunflower is grown mainly for its seeds, which constitute one of the main sources of edible oil in the world and an important element of human and animal diets.

A hardy, easy-to-grow plant

The sunflower is tolerant of drought, wet conditions and frost. It can grow in both intertropical and temperate regions. It adapts to various types of soil, whether they are sandy or clay. It is, however, intolerant to salt.

An annual plant, it reproduces naturally through pollination. As sunflowers require a long season to reach maturity, the seeds are generally sown in May. They need to be buried fairly deep (up to 10 centimetres) or in soil which is sufficiently moist to allow them to germinate. Weeds must be removed once the sunflower begins to grow, as it is unable to tolerate competition. The plant is mature when the underneath of the inflorescence is yellow and the bracts (the small leaves on the inflorescence) turn brown. The sunflower is harvested in October, when the water content of the seeds is lower than in summer and the seeds are therefore more favourable to the production of oil.

An inflorescence with thousands of flowers

The sunflower belongs to the family of Composites or Asteraceae, along with the dandelion and the thistle. The inflorescence, called the capitulum, is composed of many tiny flowers. Although it may appear simple, the sunflower’s capitulum contains thousands of flowers (up to 20 000) arranged side by side, forming a flat disk surrounded by yellow petals. The colour of the flowers can vary from lemon yellow to a reddish-orange and the disk which they form can measure up to 50 centimetres in diameter.

After the flowers have been fertilised, greyish green or black oval-shaped seeds develop. The seeds are protected by a grey or black shell, sometimes with black and white stripes. If fertilisation does not occur, the shell remains empty.

The plant’s stem usually measures between 1 and 2 metres, but can reach up to 5 metres. Its leaves are petiolate (they are connected to the plant by a small stem), triangular and serrated.

Common and scientific names

The common French name tournesol and the Spanish name girasol, come from a legend that the flowers turn to track the movement of the sun during the day. Its scientific name Helianthus, from the Greek 'helios', sun and 'anthos', flower, refers to the shape of the flower resembling that of the sun. The English and German names are literal translations of the scientific name: sunflower and Sonnenblume.