Sunflower
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Sunflower: Helianthus. Since the publication of Volume III some progress has been made in the study and breeding of sunflowers, and a brief account of the principal results follows: The investigations of A. H. Church, of Oxford, have shown that the typical unbranched monocephalous sunflower (Helianthus annuus, Linn.), which is not known in the wild state, has come down to us unchanged from ancient times, and existed in cultivation in pre-Columbian America. It was grown at Madrid and described by Dodonaeus as early as 1567. (American Naturalist, XLIX (1915), page 609). It is found that "marking factors" exist in rays of annual sunflowers, which give rise to different patterns when the anthocyan colors are introduced. The system of markings in H. annuus and varieties is quite different from that in H. cucumerifolius (or H. debilis var.) and varieties; thus the red varieties of H. cucumerifolius produced by Herb, of Naples, have rays reddened at the end, or have a red stripe down the middle of the ray, or may have the whole upper surface of ray deep brownish pink, and the under side entirely clear light sulfur-yellow. (Journal of Heredity, VI (1915), page 542). In a culture of red sunflowers (H. annuus, variety) at Boulder, Colorado, a collarette form has been obtained in some numbers, both in the chestnut and wine-red colors. The ray-florets have extra lobes, which are small and directed inward, the structure being like that of the collarette dahlia, though less regular. The type will doubtless be improved in course of time. (Gardeners' Chronicle, November 6, 1915, page 295.) Varieties are now obtained, but have not yet been sufficiently selected and isolated, with two or more rows of rays, in the manner of the star dahlias. It is hoped that some very good forms of the red sunflower will be developed along these lines. A new form of the wine-red sunflower has the bicolor pattern, with the background pale (dilute) orange instead of primrose. This gives, in certain cases, an exceedingly rich and bright color. By crossing the silky-haired H. argophyllus with vinous H. annuus, and again crossing the resulting plants with vinous H. annuus, a very pretty new hybrid has been obtained, the rays very pale yellow, tinted with vinous or with a broad ring of color at the base. It has the H. argophyllus foliage. As early as 1896 (Bulletin Torrey Botanical Club, vol. 23, page 357) hybrids between annual and perennial sunflowers were recorded, but without details. The hybrid H. annuus x H. scaberrimus (rigidus) was listed by Thellung in 1913. In 1913 Leonard Sutton in England used the pollen of H. rigidus (H. scaberrimus) on the red variety of H. annuus, and obtained fertile seed. The F1 had the characters of the perennial parent, but Sutton reports that an F2 plant has been obtained with small streaks and splashes of red. In 1914 Mrs. Cockerell used the pollen of the perennial H. pumilus on vinous H. annuus, and obtained seeds which produced plants in 1915. These resembled the perennial parent, and formed rosettes only during the first season. An attempt to force these into flower in the greenhouse in the winter of 1915-1916 totally failed; but three seeds of the original lot placed in a coldframe early in 1916 produced plants, one of which is a rosette, while the other two have formed no rosette, and have flowered the first season, like an annual. The largest of the first lot of plants from the H. pumilus x H. annuus cross flowered about the middle of July, 1916, and in its mature form showed a curious combination of characters. The rays, however, were entirely without red, and as is usual with perennials, gave a red color with caustic potash. (Since this was written, one of the hybrids has flowered showing the collarette character, and the lobes forming the collarette are largely red.) This hybrid plant has a curiously close resemblance to the horticultural form known as Daniel Dewar. The broad leaves with well-developed petioles are, however, like those of H. pumilus and H. annuus, not Daniel Dewar. The strongly serrate margins resemble H. annuus. At the present time the hybrids between annual and perennial sunflowers present many problems, and are exceedingly puzzling. It seems probable that results of considerable botanical and horticultural interest will eventually be obtained. S. Alexander of Michigan has made an elaborate study of the forms of perennial sunflowers growing in his region. He finds that only part of the species are perennial in the strictest sense, the others reproducing by underground branches, having no permanent budding crowns. He also finds that the forms are extremely diverse and has recognized over 600 minor species, differing in a variety of characters. This great diversity of character should afford the basis for many interesting horticultural forms. The nature of these lesser types, from the standpoint of genetics, has not been ascertained. If crossing has taken place, the various combinations arising may have been perpetuated and increased by the system of vegetative reproduction by "earth-branches," which would give us areas covered with plants of the same composition, constituting apparently fixed and constant "species." Alexander finds, however, that the true stationary perennials present a great diversity of forms, though they appear to be far less numerous than are the migrators.
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The sunflower (Helianthus annuus) is an annual plant native to the Americas in the family Asteraceae, with a large flowering head (inflorescence). The stem of the flower can grow up to 3 metres tall, with the flower head reaching 30 cm in diameter. The term "sunflower" is also used to refer to all plants of the genus Helianthus, many of which are perennial plants.
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Description
What is usually called the flower is actually a head (formally composite flower) of numerous flowers (florets) crowded together. The outer flowers are the ray florets and can be yellow, maroon, orange, or other colors, and are sterile. The florets inside the circular head are called disc florets. The disc florets mature into what are traditionally called "sunflower seeds", but are actually the fruit (an achene) of the plant. The true seeds are encased in an inedible husk.
The florets within this cluster are arranged spirally. Typically each floret is oriented toward the next by approximately the golden angle, 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 1 direction and 55 in the other; on a very large sunflower you may see 89 in one direction and 144 in the other.
Heliotropism
Sunflowers in the bud stage exhibit heliotropism. At sunrise, the faces of most sunflowers are turned towards the east. Over the course of the day, they move to track the sun from east to west, while at night they return to an eastward orientation. This motion is performed by motor cells in the pulvinus, a flexible segment of the stem just below the bud. As the bud stage ends, the stem stiffens and the blooming stage is reached.
Sunflowers in the blooming stage are not heliotropic anymore. The stem has frozen, typically in an eastward orientation. The stem and leaves lose their green color.
The wild sunflower typically does not turn toward the sun; its flowering heads may face many directions when mature. However, the leaves typically exhibit some heliotropism.
Cultivation and uses
Sunflowers are native to the Americas. There is some debate about where the sunflower was first domesticated. The earliest known examples of a fully domesticated sunflower were found at the Hayes site in Tennessee that date back to around 2300 B.C. There were also other remains found at the Olmec site of San Andrés dating some time before 2100 B.C. The Incas used the sunflower as an image of their sun god. Gold images of the flower, as well as seeds, were taken back to Europe early in the 16th century.
The Giant sunflower (Helianthus giganteus) is native to the Eastern United States. They can grow to be between 3 and 12 feet tall. They can grow from Ontario to Minnesota and Kentucky to Georgia. Their flower heads can be between 2 to 3 inches wide. They are most commonly found in valleys with wet meadows or swamps. The Giant sunflower grows between July and October.
To grow well, sunflowers need full sun. They grow best in fertile, moist, well-d rained soil with a lot of mulch. In commercial planting, seeds are planted 45 cm (1.5') apart and 2.5 cm (1") deep.
Sunflower "whole seed" (fruit) is sold as snacks and can be processed into a peanut butter alternative, Sunbutter, especially in China, Russia, the United States, the Middle East and Europe. It is also sold as food for birds and can be used directly in cooking and salads.
Sunflower oil, extracted from the seeds, is used for cooking, as a carrier oil and to produce biodiesel, for which it is less expensive than the olive product. A range of sunflower varieties exist with differing fatty acid compositions; some 'high oleic' types contain a higher level of healthy monounsaturated fats in their oil than even olive oil.
During the 18th Century, the use of sunflower oil became very popular in Europe, particularly with members of the Russian Orthodox Church because sunflower oil was one of the few oils that was not prohibited during Lent.
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. Sunflowers also produce latex and are the subject of experiments to improve their suitability as an alternative crop for producing hypoallergenic rubber.
For farmers not intending to grow it, the sunflower is considered a noxious weed. The wild variety will grow unwanted in corn and soybean fields which can have a negative impact on yields.
Trivia
- The sunflower is the state flower of the U.S. state of Kansas, and one of the city flowers of Kitakyushu, Japan.
- 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).
- The sunflower is often used as a symbol of green ideology, much as the red rose is a symbol of socialism or social democracy. The sunflower is also the symbol of the Vegan Society.
Flower formation
1. The first stage of the flower formation
2. The flower is still covered, but faces the sun
3. The flower is nearly completely exposed
4. The flower is completely exposed
Gallery
Sunflowers in Manila, Philippines
Sunflowers
Bumble bee sampling Sunflower nectar
Sunflowers growing near Fargo, North Dakota
Lone sunflower about 2 m (6 ft, 6') tall
Sunflower seedlings, just three days after germination
Sunflower field in Eastern Bulgaria
Sunflower Profile
Sunflower and pollinator
Large Russian Sunflower
Sunflower
Close-up of sunflower.
The Netherlands, June 2006
A field of Sunflowers in the Canton de Genève in Switzerland
Fruiting head
Sunflower seeds in many variations and sizes.
Sunflower close-up.
Red sunflowers.
Hybrid Sunflower
Small Sunflower
See also
Notes
References
- Pope, Kevin; Pohl, Mary E. D.; Jones, John G.; Lentz, 3 David L.; von Nagy, Christopher; Vega, Francisco J.; Quitmyer Irvy R.; "Origin and Environmental Setting of Ancient Agriculture in the Lowlands of Mesoamerica", Science, 18 May 2001:Vol. 292. no. 5520, pp. 1370 - 1373.
- Shosteck, Robt. 1974. Flowers and Plants. An International Lexicon with Biographical Notes. Quadrangle/The New York Times Book Co. 329 pp.
- Wood, Marcia. June 2002. "Sunflower Rubber?" Agricultural Research. USDA. [1]
