Sunflowers
The common sunflower (Helianthus annuus) is a species of large annual forb of the daisy family Asteraceae
The genus name is derived from the Greek hḗlios 'sun' and ánthos 'flower'
The common sunflower is harvested for its edible oily seeds which are used in the production of cooking oil, as well as other uses such as food for livestock, bird food, and planting in domestic gardens for aesthetics. Wild plants are known for their multiple flower heads, whereas the domestic sunflower often possesses a single large flower head atop an unbranched stem
The plant has an erect rough-hairy stem, reaching typical heights of 3 metres (10 feet)
The tallest sunflower on record achieved 9.17 m (30 ft 1 in)
Sunflower leaves are broad, coarsely toothed, rough and mostly alternate; those near the bottom are largest and commonly heart-shaped
The plant flowers in summer
What is often called the "flower" of the sunflower is actually a "flower head" (pseudanthium) of numerous small individual five-petaled flowers ("florets")
The outer flowers, which resemble petals, are called ray flowers. Each "petal" consists of a ligule composed of fused petals of an asymmetrical ray flower. They may be yellow, red, orange, or other colors. The spirally arranged flowers in the center of the head are called disk flowers - These mature into fruit (sunflower "seeds")
Young sunflowers orient themselves in the direction of the sun. At dawn the head of the flower faces east and moves west throughout the day. When sunflowers reach full maturity they no longer follow the sun, and continuously face east
Generally, each floret is oriented toward the next by approximately the golden angle, 137.5°, producing a pattern of interconnecting spirals, where the number of left spirals and the number of right spirals are successive Fibonacci numbers. Typically, there are 34 spirals in one direction and 55 in the other - This pattern produces the most efficient packing of seeds mathematically possible within the flower head
Common sunflower was one of several plants cultivated by Native Americans in prehistoric North America
Sunflower "whole seed" (fruit) are sold as a snack food, raw or after roasting in ovens, with or without salt and/or seasonings added. Sunflower seeds can be processed into a peanut butter alternative
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
Helianthus annuus can be used in phytoremediation to extract pollutants from soil such as lead and other heavy metals, such as cadmium, zinc, cesium, strontium, and uranium. The phytoremediation process was used after the Chernobyl disaster
Modern stories often claim that in Greek mythology, the nymph Clytie transformed into a sunflower when she pined after her former lover Helios, the god of the sun
The flowers are the subject of Vincent van Gogh's Sunflowers series of still-life paintings
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