Sunflower

An annual herb with a stout, straight, stiffly hairy and usually spotted stem, 1–3 m tall. The large leaves are mostly alternate on long stalks, ovate with a pointed tip and heart-shaped base, toothed at the margin and hairy white on both surfaces. What looks like a single flower is in fact a head (capitulum) made of many florets: the outer ring of yellow ray florets is sterile, while the central disc florets are bisexual, purplish-pink, and set the fruit — the achene that holds the seed — after pollination. The head is 7–20 cm across (over 30 cm in some cultivars). Young heads show heliotropism, tracking the sun from morning to evening; mature heads usually settle facing east.

The sunflower is native to North America and was domesticated long ago; indigenous peoples used its seeds for over 4,000 years. In the 16th century the seed reached Europe and then spread worldwide. Today sunflower is one of the world's most important oil crops (after soybean, rapeseed and others); leading producers include Russia, Ukraine, Argentina and China. In Vietnam, sunflowers are grown for ornament and tourism (flower fields in Nghệ An, Đà Lạt and the Central Highlands) and for roasting seeds. The seeds contain about 40–50% oil rich in unsaturated fatty acids (linoleic and oleic) and vitamin E; the oil cake is used as animal feed.