Sunflower

Sunflower, common name for annual and perennial herbs of a genus of the family of composite flowers. The genus, which contains about 67 species, is thought to be native to South America originally, although sunflowers are now distributed almost worldwide. Some of the tall-growing forms may attain a height of 3 m (12 ft). The large, solitary blossom, sometimes as large as a meter in diameter, is composed of yellow ray flowers and a central disk of either yellow, brown, or purple flowers, depending on the species. The daily orientation of the flower to the sun is a direct result of differential growth of the stem. A plant-growth regulator, or auxin, accumulates on the shaded side of a plant when conditions of unequal light prevail. Because of this accumulation, the darker side grows faster than the sunlit side. Thus, the stem bends toward the sun.

The plants are cultivated for their seeds. Refined sunflower-seed oil is edible and considered by many equal in quality to olive oil. Cruder sunflower oil is used for making soap and candles. The oil cakes (solid residues after oil is expressed) are used as cattle feed. The raw seeds are used in poultry mixes and are consumed by humans as well. The roots of one species, also called Jerusalem artichoke (see Artichoke, Jerusalem), may be eaten boiled, stewed, or baked in pies.

Scientific classification: Sunflowers make up the genus Helianthus and belong to the family Asteraceae (formerly Compositae). The Jerusalem artichoke is classified as Helianthus tuberosus.