History of the Sunflower
Sunflowers display bright yellow colors.
Scientific classificationKingdom: PlantaeDivision: MagnoliophytaClass: MagnoliopsidaOrder:
AsteralesFamily: AsteraceaeGenus: HelianthusSpecies: annuus
Binomial name: Helianthus annuus
The sunflower (Helianthus annuus) is an annual plant in the Family Asteraceae
with a large flower head (inflorescence). The stem of the flower can grow up
to 3 metres tall, with the flower head reaching 30cm in diameter. The sunflower
is notable for turning to face the Sun, a behavior known as heliotropism.
History
Sunflowers are native to the Americas, and were domesticated around 1000 B.C.
Francisco Pizarro found the Inca subjects venerating the sunflower as an image
of their sun god, and gold images of the "flower" as well as seeds
were taken back to Europe early in the 16th century. Helianthus is from the
Greek for "sunflower".
Description
The term "sunflower" is also used to refer to all plants of the genus
Helianthus, many of which are perennial plants.
What is called the flower is actually a head (formerly composite flower) of
numerous flowers crowded together. The outer flowers are the ray florets and
can be yellow, maroon, orange, or other colors. These flowers are sterile.
The flowers that fill the circular head inside the ray flowers are called disc
florets. The arrangement of florets within this cluster is typically such that
each is separated from the next by approximately the golden angle, producing
a pattern of spirals where the number of left spirals and the number of right
spirals are successive Fibonacci numbers. The disc florets mature into "seeds".
However, what we commonly call the seeds are actually the fruit (an achene)
of the plant, with the true seeds encased in an inedible husk.
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| Sunflowers being grown near Fargo North Dakota. Heliotropism |
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| Development Stages of a Sunflower | |||
To grow well, sunflowers need full sun. They grow best in fertile, moist, well-drained soil with a lot of mulch. Seeds should be 45 cm (1.5') apart and planted 2.5 cm (1") deep.
Sunflower "whole seeds" (fruit) are sold as snacks, especially in the United States and Europe, and as food for birds. Sunflower oil, extracted from the seeds, is used for cooking (but is less cardiohealthy than olive oil), as a carrier oil and is used to produce biodiesel, for which it is less expensive than the olive product. 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. There are also new breeds of sunflowers which are transgenic, so that they are resistant to some diseases. Sunflowers also produce latex and are the subject of experiments to improve their suitability as an alternative crop for producing hypoallergenic rubber.
The sunflower is the state flower of the U.S. state of Kansas, and one of the city flowers of Kitakyushu.
The Jerusalem artichoke (Helianthus tuberosa) is related to the sunflower. The Mexican sunflower is Tithonia rotundifolia. False sunflower refers to plants of the genus Heliopsis.
Scientific literature reports, from 1567, that a 12 m (40'), traditional, single-head, sunflower plant was grown in Padua. The same seed lot grew almost 8 m (24') at other times and places (e.g. Madrid). Much more recent feats (past score years) of over 8 m (25') have been achieved in both Netherlands and Canada (Ontario).