Thecommon sunflower (Helianthus annuus) is a species of largeannualforb of the daisy familyAsteraceae. The common sunflower is harvested for itsedible oily seeds, which are often eaten as asnack food. They are also used in the production of cooking oil, as food for livestock, asbird food, and as a plantings 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).[3] Sunflower leaves are broad, coarsely toothed, rough and mostly alternate; those near the bottom are largest and commonlyheart-shaped.[4]
The plant flowers in summer. What is often called the "flower" of the sunflower is actually a "flower head" (pseudanthium), 7.5–12.5 centimetres (3–5 in) wide,[4] of numerous small individual five-petaled flowers ("florets"). The outer flowers, which resemble petals, are calledray flowers. Each "petal" consists of aligule composed of fused petals of an asymmetrical ray flower. They are sexually sterile and may be yellow, red, orange, or other colors. The spirally arranged flowers in the center of the head are calleddisk flowers. These mature into fruit (sunflower "seeds").
Theprairie sunflower (H. petiolaris) is similar in appearance to the wild common sunflower; the scales in its central disk are tipped by white hairs.[4]
Flower heads facing east, away from the late afternoon sun
A common misconception is that flowering sunflower headstrack the Sun across the sky. Although immature flower buds exhibit this behaviour, the mature flowering heads point in a fixed (and typically easterly) direction throughout the day.[5][6] This old misconception was disputed in 1597 by the English botanistJohn Gerard, who grew sunflowers in his famous herbal garden: "[some] have reported it to turn with the Sun, the which I could never observe, although I have endeavored to find out the truth of it."[7] The uniform alignment of sunflower heads in a field might give some people the false impression that the flowers are tracking the Sun.
This alignment results fromheliotropism in an earlier development stage, the young flower stage, before full maturity of flower heads (anthesis).[8] 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. Young flowers reorient overnight to face east in anticipation of the morning. Their heliotropic motion is acircadian rhythm, synchronized by the sun, which continues if the sun disappears on cloudy days or if plants are moved to constant light.[9] They are able to regulate their circadian rhythm in response to the blue-light emitted by a light source.[9] If a sunflower plant in the bud stage is rotated 180°, the bud will be turning away from the sun for a few days, as resynchronization with the sun takes time.[10]
When growth of the flower stalk stops and the flower is mature, the heliotropism also stops and the flower faces east from that moment onward. This eastward orientation allows rapid warming in the morning, and as a result, an increase in pollinator visits.[9] Sunflowers do not have apulvinus below theirinflorescence. A pulvinus is a flexible segment in the leaf stalks (petiole) of some plant species and functions as a 'joint'. It effectuates leaf motion due to reversible changes inturgor pressure which occurs without growth. The sensitive plant's closing leaves are a good example of reversible leaf movement via pulvinuli.
Generally, each floret is oriented toward the next by approximately thegolden angle, 137.5°, producing a pattern of interconnectingspirals, where the number of left spirals and the number of right spirals are successiveFibonacci numbers. Typically, there are 34 spirals in one direction and 55 in the other; however, in a very large sunflower head there could be 89 in one direction and 144 in the other.[11][12][13] This pattern produces the most efficient packing of seeds mathematically possible within the flower head.[14][15][16]
A model for the pattern offlorets in the head of a sunflower was proposed by H. Vogel in 1979.[17] This is expressed inpolar coordinates
where θ is the angle,r is the radius or distance from the center, andn is the index number of the floret andc is a constant scaling factor. It is a form ofFermat's spiral. The angle 137.5° is related to thegolden ratio (55/144 of a circular angle, where 55 and 144 are Fibonacci numbers) and gives a close packing of florets. This model has been used to produce computer generated representations of sunflowers.[18]
In thebinomial nameHelianthus annuus, the genus name is derived from the Greekἥλιος : hḗlios 'sun' andἄνθος : ánthos 'flower'. The species nameannuus means 'annual' in Latin.
The plant was first domesticated in the Americas. Sunflower seeds were brought to Europefrom the Americas in the 16th century, where, along withsunflower oil, they became a widespread cooking ingredient. With time, the bulk of industrial-scale production has shifted to Eastern Europe, and (as of 2020[update]) Russia and Ukraine together produce over half of worldwide seed production.
Sunflowers grow best in fertile, moist, well-drained soil with heavymulch. They often appear on dry open areas and foothills.[4] Outside of cultivation, the common sunflower is found on moist clay-based soils in areas with climates similar to Texas. In contrast, the relatedHelianthus debilis andHelianthus petiolaris are found on drier, sandier soils.[22]
The precise native range is difficult to determine. According toPlants of the World Online (POWO), it is native to Arizona, California, and Nevada in the present-day United States and to all parts of Mexico except the Gulf Coast and southeast.[23] Though not giving much detail, the Missouri Botanical Garden Plant Finder also lists it as native to the Western United States and Canada.[24] The information published by the Biota of North America Program (BONAP) largely agrees with this, showing the common sunflower as native to states west of the Mississippi, though also listed as a noxious weed in Iowa, Minnesota, and Texas.[25] Regardless of its original range, it can now be found in almost every part of the world that is not tropical, desert, or tundra.[23]
One of the major threats that sunflowers face today isFusarium, a filamentous fungus that is found largely in soil and plants. It is a pathogen that over the years has caused an increasing amount of damage and loss of sunflower crops, some as extensive as 80% of damaged crops.[26]
Downy mildew is another disease to which sunflowers are susceptible. Its susceptibility to downy mildew is particularly high due to the sunflower's way of growth and development. Sunflower seeds are generally planted only an inch deep in the ground. When such shallow planting is done in moist and soaked earth or soil, it increases the chances of diseases such as downy mildew.
Another major threat to sunflower crops arebroomrapes, a family of plants whichparasitize the roots of various other plants, including sunflowers. Damage and loss to sunflower crops as a result of broomrape can be as high as 100%.[27]
Common sunflower was one of several plants cultivated byNative Americans inprehistoric North America as part of theEastern Agricultural Complex, which also included corn, beans, squash, and a variety of other crops.[28] Although it was commonly accepted that the sunflower was first domesticated in what is now the southeastern US, roughly 5,000 years ago,[29] there is evidence that it was first domesticated in Mexico[30] around 2600 BCE. These crops were found inTabasco, Mexico, at the San Andres dig site. The earliest known examples in the US of a fully domesticated sunflower have been found inTennessee, and date to around 2300 BCE.[31] Other very early examples come from rockshelter sites in Eastern Kentucky.[32] Manyindigenous American peoples used the sunflower as the symbol of theirsolar deity, including theAztecs and theOtomi of Mexico and theIncas in South America. In 1510, early Spanish explorers encountered the sunflower in the Americas and carried its seeds back to Europe.[33] Of the four plants known to have been domesticated in eastern North America[34] and to have become important agricultural commodities, the sunflower is currently the most economically important.[citation needed]
Research of phylogeographic relations and population demographic patterns across sunflowers has demonstrated that earlier cultivated sunflowers form aclade from wild populations from theGreat Plains, which indicates that there was a single domestication event in central North America. Following the cultivated sunflower's origin, it may have gone through significant bottlenecks dating back to ~5,000 years ago.[35]
In the 16th century the first crop breeds were broughtfrom America to Europe by explorers.[36] Domestic sunflower seeds have been found in Mexico, dating to 2100 BCE. Native American people grew sunflowers as a crop from Mexico to Southern Canada.[36] They then were introduced to theRussian Empire, where oilseed cultivators were located, and the flowers were developed and grown on an industrial scale. The Russian Empire reintroduced this oilseed cultivation process to North America in the mid-20th century; North America began their commercial era of sunflower production and breeding.[9] New breeds of theHelianthus spp. began to become more prominent in new geographical areas. During the 18th century, the use of sunflower oil became very popular in Russia, particularly with members of theRussian Orthodox Church, because only plant-based fats were allowed duringLent, according tofasting traditions.[37] In the early 19th century, it was first commercialized in thevillage of Alexeyevka inVoronezh Governorate by the merchant named Daniil Bokaryov, who developed a technology suitable for its large-scale extraction, and quickly spread around. The town's coat of arms has included an image of a sunflower ever since.[citation needed]
Researchers have analyzed the impact of various nitrogen-based fertilizers on the growth of sunflowers.Ammonium nitrate was found to produce better nitrogen absorption thanurea, which performed better in low-temperature areas.[39]
In today's market, most of the sunflower seeds provided or grown by farmers are hybrids. Hybrids or hybridized sunflowers are produced by cross-breeding different types and species, for example cultivated sunflowers with wild species. By doing so, new genetic recombinations are obtained ultimately leading to the production of new hybrid species. These hybrid species generally have a higher fitness and carry properties or characteristics that farmers look for, such as resistance to pathogens.[26]
Hybrid,Helianthus annuus dwarf2 does not contain the hormone gibberellin and does not display heliotropic behavior. Plants treated with an external application of the hormone display a temporary restoration of elongation growth patterns. This growth pattern diminished by 35% 7–14 days after final treatment.[9]
Hybrid male sterile and male fertile flowers that display heterogeneity have a low crossover of honeybee visitation. Sensory cues such as pollen odor, diameter of seed head, and height may influence pollinator visitation of pollinators that display constancy behavior patterns.[43]
Sunflowers are grown as ornamentals in a domestic setting. Being easy to grow and producing spectacular results in any good, moist soil in full sun, they are a favourite subject for children. A large number of cultivars, of varying size and color, are now available to grow from seed. The following arecultivars of sunflowers (those markedagm have gained theRoyal Horticultural Society'sAward of Garden Merit):[44]
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 butter. It is also sold as food for birds and can be used directly in cooking and salads. Native Americans had multiple uses for sunflowers in the past, such as in bread, medical ointments, dyes and body paints.[57]
Sunflower oil, extracted from the seeds, isused for cooking, as acarrier oil and to producemargarine andbiodiesel, as it is cheaper thanolive oil. A range of sunflower varieties exist with differing fatty acid compositions; some "high-oleic" types contain a higher level of monounsaturated fats in their oil than even olive oil. The oil is also sometimes used in soap.[58] AfterWorld War I, during theRussian Civil War, people in Ukraine used sunflower seed oil in lamps as a substitute forkerosene due to shortages. The light from such a lamp has been described as "miserable" and "smoky".[59]
The cake remaining after the seeds have been processed for oil is used as livestock feed.[60] The hulls resulting from the dehulling of the seeds before oil extraction can also be fed to domestic animals.[61] Some recently developedcultivars have drooping heads. These cultivars are less attractive togardeners growing the flowers asornamental plants, but appeal to farmers, because they reduce bird damage and losses from someplant diseases. Sunflowers also producelatex, and are the subject of experiments to improve their suitability as an alternative crop for producinghypoallergenic rubber.
Traditionally, several Native American groups planted sunflowers on the north edges of their gardens as a "fourth sister" to the better-knownthree sisters combination ofcorn,beans, andsquash.[62] Annual species are often planted for theirallelopathic properties.[63] It was also used by Native Americans to dress hair.[58] Among theZuni people, the fresh or dried root is chewed by themedicine man before sucking venom from a snakebite and applying apoultice to the wound.[64] This compound poultice of the root is applied with much ceremony to rattlesnake bites.[65]
However, for commercial farmers growing other commodity crops, the wild sunflower is often considered a weed. Especially in the Midwestern US, wild (perennial) species are often found in corn and soybean fields and can decrease yields. The decrease in yield can be attributed to the production of phenolic compounds which are used to reduce competition for nutrients in nutrient-poor growing areas of the common sunflower.[66]
TheZuni people use the blossoms ceremonially for anthropic worship.[73] Sunflowers were also worshipped by the Incas because they viewed it as a symbol for the Sun.[74]
Stories ofClytie thenymph who was spurned by her former loverHelios end with her transformed into what may be translated as sunflower. However, the plant inGreek mythology may be, "partly pale and partly red, and very like a violet". The plant described also exhibitsheliotropism, with its face turning towards the sun. This plant may be a species in the genus heliotrope (Heliotropium).[75] However, less commonly it is identified as the common marigold (Calendula officinalis).[76]
During the 19th century, it was believed that nearby plants of the species would protect a home from malaria.[58] The flowers are the subject ofVincent van Gogh'sSunflowers series of still-life paintings.
In July 2015,viable seeds were acquired from the field whereMalaysia Airlines Flight 17 crashed on a year earlier and were grown intribute to the 15 Dutch residents ofHilversum who were killed.[77] Earlier that year,Fairfax chief correspondentPaul McGeough and photographerKate Geraghty had collected 1.5 kg of sunflower seeds from the wreck sitefor family and friends of the 38 Australian victims, who aimed to give them a poignant symbol of hope.[78]
On 13 May 2021, during the National Costume competition of theMiss Universe 2020 beauty pageant,Miss Dominican RepublicKimberly Jiménez wore a "Goddess of Sunflowers" costume covered in gold and yellow rhinestones[79] that included several real sunflowers sewn onto the fabric.
The sunflower is the national flower ofUkraine.[80] Ukrainians used sunflower as a main source ofcooking oil instead of butter orlard forbidden by theOrthodox Church when observingLent. They were also planted to serve asbioremediation inChernobyl. In June 1996, U.S., Russian, and Ukrainian officials planted sunflowers at thePervomaysk missile base where Sovietnuclear weapons were formerly placed.[71] During theRussian invasion of Ukraine, a video widely shared on social media showed a Ukrainian woman confronting a Russian soldier, telling the latter to "take these seeds and put them in your pockets so at least sunflowers will grow when you all lie down here".[81] The sunflower has since become a global symbol of resistance, unity, and hope.[82]
During the late 19th century, the flower was used as the symbol of theAesthetic Movement.
The sunflower was chosen as the symbol of theSpiritualist Church, for many reasons, but mostly because of the (false) belief that the flowers turn toward the sun as "Spiritualism turns toward the light of truth". Modern Spiritualists often have art or jewelry with sunflower designs.[83]
The sunflower is often used as a symbol ofgreen ideology. The flower is also the symbol of theVegan Society.
^Hangarter, Roger P."Solar tracking: sunflower plants".Plants-In-Motion website. Indiana University. Retrieved22 August 2012.Many people are under the misconception that the flower heads of the cultivated sunflower (Helianthus annuus) track the sun... Immature sunflower flower heads do exhibit solar tracking and on sunny days the buds will track the sun across the sky from east to west... However, as the flower bud matures and blossoms, the stem stiffens and the flower head becomes fixed facing the eastward direction."
^Gerard, John (1597).Herball, or Generall Historie of Plantes. London: John Norton. pp. 612–614. Retrieved8 August 2012. Popular botany book in 17th century England
^Knott, Ron (30 October 2010)."Fibonacci Numbers and Nature".Department of Computer Science. University of Surrey. Archived fromthe original on 7 September 2009. Retrieved31 January 2011.
^"Helianthus annuus".Plant Finder. St. Louis, Missouri: Missouri Botanical Garden. Retrieved4 October 2023.
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^abGontcharov, SV. Antonova, TS. and Saukova, SL. 2006. Sunflower breeding for resistance to fusarium. Helia [accessed 14 September 2014]; 29 (45): 49–54.
^Putt, E.D. (1997). "Early history of sunflower". In A.A. Schneiter (ed.).Sunflower Technology and Production. Agronomy Series. Vol. 35. Madison, Wisconsin: American Society of Agronomy. pp. 1–19.
^Debaeke, Philippe; Izquierdo, Natalia G. (1 January 2021), Sadras, Victor O.; Calderini, Daniel F. (eds.),"Chapter 16 – Sunflower",Crop Physiology Case Histories for Major Crops, Academic Press, pp. 482–517,doi:10.1016/b978-0-12-819194-1.00016-5,ISBN978-0-12-819194-1,S2CID243584066, retrieved4 July 2023,In most countries, sunflower is usually recommended to be grown in 3–4 years rotations, generally with cereals (e.g. wheat, barley, maize and sorghum), soybean, oilseed rape and grain legumes
^Pelczar, Rita. (1993) The Prodigal Sunflower.American Horticulturist 72(8).
^abcNiering, William A.; Olmstead, Nancy C. (1985) [1979].The Audubon Society Field Guide to North American Wildflowers, Eastern Region. Knopf. p. 384.ISBN0-394-50432-1.
^Neufeld, Dietrich.A Russian Dance of Death: Revolution and Civil War in the Ukraine. Hyperion: Winnipeg, Canada (1980), p. 50.
^Heuzé V., Tran G., Hassoun P., Lessire M., Lebas F., 2016. Sunflower meal. Feedipedia, a programme by INRA, CIRAD, AFZ and FAO.https://www.feedipedia.org/node/732
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^Camazine, Scott and Robert A. Bye (1980) A Study of the Medical Ethnobotany of the Zuni Indians of New Mexico.Journal of Ethnopharmacology 2:365–388 (p.375)
^Stevenson, Matilda Coxe (1915) Ethnobotany of the Zuni Indians. SI-BAE Annual Report No. 30 (p.53-54)
^Awtry-Smith, Marilyn J. The Symbol of Spiritualism: The Sunflower. Reprinted from theNew Educational Course on Modern Spiritualism. Appendix IV inTalking to the Other Side: A History of Modern Spiritualism and Mediumship, ed. by Todd Jay Leonard.ISBN0-595-36353-9.
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