To grow well, sunflowers need full sun. They grow best in fertile, moist, well-drained soil with a lot of mulch. In commercial planting, seeds are planted 45 cm (1.5 ft) apart and 2.5 cm (1 in) deep. Sunflower "whole seed" (fruit) are sold as a snack food, after roasting in ovens, with or without salt added. Sunflowers can be processed into a peanut butter alternative, sunbutter. In Germany, it is mixed together with rye flour to make Sonnenblumenkernbrot (literally: sunflower whole seed bread), which is quite popular in German-speaking Europe. It is also sold as food for birds and can be used directly in cooking and salads.
Sunflower oil, extracted from the seeds, is used for cooking, as a carrier oil and to produce margarine and biodiesel, as it is cheaper than olive oil. A range of sunflower varieties exist with differing fatty acid compositions; some 'high oleic' types contain a higher level of healthy monounsaturated fats in their oil than even olive oil.
The cake remaining after the seeds have been processed for oil is used as a livestock feed. Some recently developed cultivars have drooping heads. These cultivars are less attractive to gardeners growing the flowers as ornamental plants, but appeal to farmers, because they reduce bird damage and losses from some plant diseases. Sunflowers also produce latex and are the subject of experiments to improve their suitability as an alternative crop for producing hypoallergenic rubber.
Traditionally, several Native American groups planted sunflowers on the north edges of their gardens as a "fourth sister" to the better known three sisters combination of corn, beans, and squash. Annual species are often planted for their allelopathic properties.
However, for commercial farmers growing commodity crops, the sunflower, like any other unwanted plant, is often considered a weed. Especially in the midwestern US, wild (perennial) species are often found in corn and soybean fields and can have a negative impact on yields.
Sunflowers may also be used to extract toxic ingredients from soil, such as lead, arsenic and uranium. They were used to remove uranium, cesium-137, and strontium-90 from soil after the Chernobyl disaster (see phytoremediation).
Source : http://en.wikipedia.org/wiki/Sunflower
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