Common Name: Woodland Sunflower

Scientific Name: Helianthus divaricatus (The generic name is from the Greek helios meaning Sun and anthos meaning flower; the species name is from the Latin divarico which means to stretch apart or spread out, referring to the ray flowers).


The Woodland Sunflower is one of the 19,000 species in 920 genera that make up the Asteraceae or Compositae Family. The characteristic feature of the family is that the flower is a composite; the circular disc-like head populated by small florets surrounded by a number of ray flowers that look like petals. Helianthus is the genus of the true sunflower, a native of North America.  It is comprised of 49 species that have been analyzed using DNA into seven series that are genetically related. Using an extrapolation of genetic substitutions or mutations per year, the sunflower species converge into a single ancestor between 11 and 15 million years ago in the Miocene Epoch of the Tertiary Period. The commercially important species is the Common Sunflower, H. annus.


Sunflowers have been cultivated by Native Americans for at least 3,000 years based on archaeological evidence from the Salts Cave in Kentucky, the only major food crop that originated in the contiguous United States. The sunflower was a mainstay of Indian life and culture. The seeds were consumed directly or were ground to make flour for cakes and bread.  The oil was extracted by pounding the seeds with a mortar into a mass that was boiled in water; the oil skimmed off and used as pomade or as a base for body paint.  The Hopi produced a purple dye from the seeds and a yellow dye from the flowers. Medicinal uses included a sunflower tea used to treat lung ailments and a leaf poultice that was applied to sores, snake bites and spider bites. The Inca people worshipped the sunflower; their priestesses were crowned with sunflowers and symbolic sunflowers fabricated from gold adorned their temples. This brought the sunflower to the attention of the gold seeking Conquistadores.


Spanish explorers brought the sunflower to Spain in about 1500. By the early 18th Century, the sunflower had spread throughout Europe as an ornamental plant. Though the extraction of oil from the sunflower was patented in England in 1716, it was not until Peter the Great saw it in Holland and brought it to Russia that sunflower oil became a viable commercial commodity. This was in part because the Russian Orthodox Church forbade the consumption of oil during Lent, the oil of the sunflower being exempt. By the early 19th Century, over 2 million acres of sunflowers were planted in Russia. In 1912, V. S. Pustovoit began a lifelong career in the breeding of sunflowers to create cultivars with high oil production in Krasnodar just north of the Caucasus Mountains of Russia.  The highest honor in the sunflower industry is the V. S. Pustovoit Award as a tribute to his scientific contributions.


The cultivars of the sunflower developed in Russia, such as the "Mammoth Russian," returned to North America in the late 19th Century, probably as a direct result of Russian immigration. Initially, the sunflower was used as silage for livestock, but in 1926, the Missouri Sunflower Growers' Association initiated the processing of sunflower oil. The production of sunflower oil in the United States expanded to over 5 million acres in the 1970's as a result of European demand, which was largely stimulated by health concerns about consuming high cholesterol animal fats.


Sunflower oil is produced by crushing sunflower seeds, which are not really seeds but the cotyledons of the sunflower embryo known as achenes.  An achene is an indehiscent (not opening at maturity) fruit that contains a loosely bound seed in its outer wall or pericarp. The oil is one of the best polyunsaturated vegetable oils as it has more double bonds in each triglyceride molecule. It is mixed with linseed oil to make soap, candles and varnishes and it is an excellent general purpose lubricant. 


There are many uses of the sunflower after the extraction of the seed oil from the achene.  The remnants of the pericarp and the non-oil solids of the seed are pressed into a high protein seedcake for feeding ruminant livestock. The pith of sunflower stems is one of the lightest substances known with a specific gravity of .028 (by comparison cork is .24). It is used in the manufacture of various flotation devices like life rings for water rescue.  The dried stems also make an excellent fuel.  The Soviets made acoustical ceiling tile from the fibers of the stem and the Chinese have experimented with using the stems to use as an additive to various fabrics including silk.


The sunflower is heliotropic; it turns to face the sun. This behavior is so marked in the sunflower that it is called girasol in Spanish, tournesol in French and was once called heliotrope in English. This evolutionary adaptation is a specific application of a more general tropism where plants turn toward a stimulus. Sunflower buds track the sun with motor cells in the pulvinus, a flexible segment of the stem at the base of the bud. As they mature, the pulvinus hardens and the stem freezes, normally in the eastward direction, toward the rising sun. 


Sunflower heads form an intriguing geometric pattern that is characterized by spirals that extend from the center outward in both the clockwise and counterclockwise direction. The spirals are formed by the achenes as they develop, their position relative to preceding achenes optimized to maximize exposure to the sun.  The angle that they form is related to the Golden Ratio, Phi, a number that is approximately 1.618034.  The Golden Ratio has the unique property that Phi-1 = 1/Phi.  The Golden Ratio is related to the Fibonacci numbers (1, 1, 2, 3, 5, 8, 13, 21 where the next number is the sum of the preceding two numbers). As one extends this ratio to infinity, the ratio of any number to the one that precedes it approaches Phi (thus 21/13 = 1.62). Because of Phi, the number of spirals in either direction on a sunflower head will always be one of the Fibonacci numbers, such as 8, 13, or 21.


Fibonacci, or Leonard of Pisa, was the son of Gugleilmo Bonnacci, the nickname stemming from a shortened "fi" for "filius" or son of Bonnacci. He is widely accredited with introducing the Arabic system of arithmetic to Italy in the 13th Century with the book Liber Abbaci, The Book of Calculations. The eponymous Fibonacci numbers are the answer to one of the exercises in the book: If a pair of rabbits is put in a field and they take a month to reach maturity and thereafter produce a new pair every month after that, how many rabbits will there be in a year. The answer follows the sequence of adding the last two numbers for twelve cycles, yielding 144 pairs.