Sunflower
Sunflowers (Helianthus annuus) are tall annuals that can reach a height of between 1.5 and 2.5m at flowering.
Sunflowers originated in subtropical and temperate zones and are more common in warmer countries such as Australia, however through selective breeding they have become highly adaptable. Anecdotal estimates suggest that 60,000 ha could be grown in southern Britain, based upon land capacity, however currently about 500 to 600 hectares are grown annually, producing about 1000 tonne of seed. Most of the seed produced is used as birdseed, but the dried stems make an excellent fuel, or fibre from the stem can be used to make paper and fine quality cloth.
Sunflower has a wide potential sowing window, with higher yields possible from earlier sowing, however they are also more susceptible to pest damage. The crop grows on most soils, preferring those that are light and well drained with a pH of 6.5 to 7.5. Seedbed preparation should leave a moist soil environment for germination and growth.
The crop is generally harvested from September to October following a growing season of around 120 days, depending mainly on summer temperatures. Yields range from 1-2.5t/ha, with average yields of 2.2t/ha from the semi-dwarf varieties that are adapted to UK conditions.
Nitrogen applications of 50-75kg/ha are generally sufficient, with deficiency symptoms showing up as reduced growth and general chlorosis. Adequate supplies of phosphorus and potash are also required.
