Sunflowers are mostly produced for its oil but also as a food crop. Oilseeds are black in colour and smaller than sunflower seeds for eating which are white and black striped. Oilseed sunflowers can be further divided into linoleic and high oleic types.
In the 1990s mid-oleic sunflower oilseeds were developed. These classifications refer to the types of fats in the seed.
Selection for high oil sunflower seed types began in 1860 in Russia where breeding programs resulted in increasing the seed oil content from 28% to almost 50%.
Oil concentration (usually expressed as a percentage of seed dry mass) determines the yield of the grains. Therefore, both seed yield and oil percentage are important to sunflower farmers. Grain oil concentration is mainly determined during the grain-filling period - a term to denote the growing and ‘fattening’ of the grain kernel.
The appropriate planting date is crucial for good seed germination, the appearance of seedlings and the optimum development of the root system. (The planting date will determine the overall growing time and therefore the time the sunflower seed has to ‘fill up’ with oil).
The actual planting dates will influence the type of sunflower that will be planted. For example, if rains are delayed and the soil is too dry, the days left until the frost starts will determine which type of sunflower seed should be selected.
The choice of seed should also consider factors such as yield, oil percentage, seed size (for non-oilseed markets), and bird resistance. Farmers should select sunflower cultivars best suited to their production area.
In South Africa, the red sunflower and Mexican sunflower type, both native species of Mexico and introduced as ornamental species in South Africa, have been declared alien invasive weeds.
The advice of a seed supplier or agricultural advisor is recommended.
By Marinda Louw