The sunflower is an annual plant belonging to the Asteraceae, which is the largest flowering plant family found in nature. The most widespread and most cultivated species is Helianthus annuus. The scientific name "Helianthus" derives from the Greek word "helios" which means sun, and "anthos" that is flower, while its common name "sunflower" derives from a particularity of this plant, which presents a remarkable heliotropism; that is, the flower moves following the movements of the sun, and in this way faces it for the whole day; this is possible thanks to the "pulvino", a filament that is found on the stem.
It is native to North America, where it was cultivated by Indians who used it for food purposes and considered it a sacred plant. The Incas considered it the symbol of the sun, they knew the nutritional properties of the seeds and obtained fibers from the leaves and the stem. It was introduced to Europe from Peru by the first European explorers in the 16th century; here it spreads mainly as an ornamental plant, thanks to its beauty and lively color; later it is also cultivated for food purposes. In the nineteenth century it spread widely in Russia. Today it is grown all over the world for food use, for the extraction of dyes, oils and medicinal substances; also in Italy it is very present and it is possible to find it above all in the central regions.
The sunflower is a herbaceous plant that has an inflorescence, that is, a set of flowers, to be precise, a flower head. The flower head is composed of two types of flowers: in the center the flowers of the disc (the brown "button") and in the periphery the flowers of the ray (what are commonly called petals and which are yellow). (usually the ones in the center) or open (the outermost ones). You can isolate them by pulling them away from the base and you can see that they have the shape of a small trumpet; this tubular body is the corolla, whose petals are welded together for most of their length, while at the upper end they separate forming denticles. The flowers of the ray are elongated; the corolla is made up of petals welded together so as to form a tongue, and it is this that gives the whole flower the appearance of a petal.
The stem is straight and robust and can reach great heights, even up to three meters, but there are also smaller varieties; the leaves are large, of a beautiful intense green, have a long petiole, are rough on both sides and are opposite up to the second-third pair, after which they are alternate. It has a long tap root on which the lateral roots are inserted.
The sunflower prefers a warm environment, the minimum recommended temperature is 12 - 14 degrees. It lives well in both sunny and semi-shaded environments, the important thing is that it has at least 4-5 hours of sunshine available. In case of strong wind it is necessary to fix bamboo poles to the stem to support it.
Sunflowers are particularly suitable for cultivation in the open ground or, for varieties that do not reach a high height, even in pots. They do not need a particular soil, the important thing is that it is fertile and deep, since the roots need space; it is preferable to mix the earth with a little peat which is a material of organic origin formed by the remains of plants or animals soaked in water, which cannot completely decompose due to the acidity of the environment. It is always good to provide a good drainage base by lightening the soil with sand or creating a layer of expanded clay of about 5 cm at the base of the pot to prevent the formation of stagnations which over time lead to root rot with the consequent death of the plant. .
They should be sown at the beginning of the spring season, from the end of March to mid-April; the seeds can be taken from the corolla when the flower has dried or they can be found at the florist or supermarket; they are to be placed in the ground in holes 3 - 4 cm deep, in rows placed at a distance of 35 - 70 cm depending on the size of the species, or sown in pots and transplanted into larger pots when the seedlings have reached 10 cm, looking for not to damage the roots.
Even if the plant tolerates the heat well, the soil must be irrigated constantly, avoiding stagnation and allowing it to absorb the water well. As for growing in pots, the sunflower must be watered every time the earth dries up, always avoiding stagnation of water that cause root rot. The first symptoms of bad watering are the failure of the buds to bloom, in fact in a suffering plant we often see that it cannot make more than one flower bloom at a time and all the other buds dry out. To avoid the abortion of the flowers it is necessary to provide the plant with a good soil with a good drainage base made of expanded clay or sand to prevent stagnation which then leads to root rot.
It is preferable to fertilize the sunflower with organic fertilizer or with a slow release fertilizer. It should be borne in mind that with its roots it is able to absorb substances from the soil even at great depths. Among the substances to be used, nitrogen is very useful, the optimal dose of which ranges from 80 to 120 kg / ha; the dose can be applied in a single time at sowing or in two times, 60% of the quantity at sowing and 40% later, generally during weeding, which consists in working the surface of the soil with the aim of eliminating weeds and allow the roots to breathe. Another substance is phosphorus; the recommended dose is 40 - 70 kg / ha and is usually distributed on the ground before processing the latter. Finally, potassium is used whose recommended dose is 50 kg / ha; this type of fertilization, however, can also be avoided since the Italian soils are mostly clayey and rich in this substance.
Sunflowers do not need large pruning, just eliminate the parts damaged by parasites and those dry or withered. If you want to favor the flowering of new flowers, it is good to eliminate the withered flowers.
The multiplication of this plant occurs by seed. It is necessary to bury the seed in two, three centimeters of well-worked and fertile earth. The sunflower ends its development cycle in 110-145 days. After 5 - 7 days from sowing, the seed germinates; in about 30 days there is the emergence of the leaves and a development of the root system, then the formation of the flower button and immediately after flowering. The period that goes from the formation of the button to the flowering can last from 25 to 30 days, during which there is a considerable growth of the plant and the flowers open in series according to a centripetal spiral; the inflorescence has elongated external flowers that can be yellow, brown or orange and are sterile, that is, they do not produce any seeds; the internal flowers are brown in color and are the ones that become seeds. Flowering occurs in summer, especially from August to October.
The sunflower is a fairly resistant plant, but it can be damaged by some parasites that hide under or inside the inflorescences and which can be fought with pesticides. It is mainly affected by parasites defined as phytophagous such as Sminthurus viridis; they feed on the content of single cells or take up portions of tissue and internal fluids, causing serious damage to the plant. Another threat is constituted by fungal diseases such as gray mold, rust, powdery mildew, stem and calatid rot, to be treated with anti-tritis products. Gray mold causes the presence on the leaves, stem and buds of a very thick gray patina that leads to withering. Rust causes yellowing of the leaves; it rarely leads to the death of the plant, which usually manages to reach maturity, slowly wasting away. Powdery mildew or bad white looks like a whitish patina covering the leaf which first turns yellow and then dries up. The rot of the stem and calatide manifests itself with a wet greenish rot and a white and cottony patina that causes the plant to wither.
It should also be remembered that insects do not cause damage to sunflowers, unlike birds and snails that frequently attack them.
Since the sunflower is presented in all its beauty in summer, it is advisable to buy them especially in this season; they are the most suitable plants to give a touch of color and to brighten up the garden and the house in the warmer months. To promote good growth it is good to prepare a rich and fertile soil, it is advisable to obtain a good already fertilized soil that will be integrated with further fertilizer during flowering.
To avoid stagnation of water it is good to drain the soil with sand or by creating a layer of expanded clay on the bottom, this is necessary to avoid the abortion of the buds that are frequent in case of bad irrigation.
The Helianthus genus includes about 100 different species; among these we must distinguish wild species and cultivated species. Wild plants are considered weeds that grow between fields and can damage crops. Those cultivable differ from each other in height, shape and color of the flowers. In addition to the cultivable species Helianthus annuus, which is the best known, Helianthus debilis is also widespread, which has medium-sized corollas, with petals ranging from ivory white to blackish. Furthermore, the Helianthus hirsutus which has small yellow flowers and can reach a height of two meters. Helianthus grosseratus, whose flower head is yellow and can reach 5 cm in diameter. Helianthus occidentalis, which has antibiotic properties. Helianthus mollis which can reach a maximum height of 1.20 meters and has dark yellow flowers.
The sunflower is present in Greek mythology. It is mentioned in the poem "The Metamorphoses" by Ovid, a Roman poet who lived between 43 BC. and 18 A.D. In this poem Ovid tells of an aquatic nymph, Clizia, in love with the sun god, Apollo. This love is not reciprocated, in fact Apollo was in love with Leucotoe, daughter of the Babylonian king Orcamo. Clizia, seized by jealousy, goes to Leucotoe's severe father and informs him of the secret relationship between his daughter and the god Apollo. Furious Orcamo orders to bury his daughter alive. The nymph, at this point, tries to finally get the consideration of Apollo, but without success. Taken by desperation, she spends her days without eating and crying and she just has to follow with her eyes the chariot of Apollo flying in the sky. After nine days Jupiter takes pity on her and transforms her into a sunflower which, changing its inclination, always follows the trend of the sun, just as the nymph in life followed Apollo.
We also find the sunflower in Italian literature, as, for example, in a poem by Eugenio Montale taken from the volume "Ossi di seppia": "Bring me the sunflower that I will transplant it / into my soil burned by the salt, / and show all the day to the mirror blues / of the sky the anxiety of his yellow face ... "
For those who believe in the meaning of flowers, the sunflower indicates joy and pride.
The sunflower (Helianthus annuus L.) is a cheerful addition to any garden. Quick and easy to grow, the sunflower looks foolproof. But, it is important to remember that planting sunflower seeds at the appropriate temperature is critical for proper germination.
Often overlooked, the correct temperature is essential for sunflower seed germination. Soil and ambient temperatures affect the number of seeds that germinate and the rate at which they grow. Sunflower seeds have an optimal temperature requirement of 70 to 78 degrees Fahrenheit, although temperatures ranging from 64 to 91 won't make a noticeable difference on productivity.
Temperatures that exceed 91 degrees Fahrenheit greatly hamper sunflower seed germination, germination rate and seed viability. Germination can occur at temperatures above 100 degrees, but is no longer possible at 113 degrees.
The sunflower plant is more tolerant of lower temperatures. Germination has occurred in temperatures up to 39 degrees Fahrenheit, but growth is more likely to occur between 46 and 50 degrees. Once germination has been set in motion, temperature dips to 23 degrees will not hinder germination.
It's about a annual herbaceous plant with taproot and numerous radicles presenting a simple stem which can reach up to 3 meters in height. The consistency of the stem is spongy, large cordiform and oval petiolate leaves branch off from it.
The sunflower flowers they are gathered in large ligulate flower heads, the exteriors yellow and the exteriors yellow-brown. the fruit is a blackish achene, widely used for food purposes. Almost impossible to find in the wild, its presence is frequent in crops, where both flowers and seeds are used in harvesting. But dwarf species are generally grown for aesthetic flowers.
Climate. Sunflowers are not particularly afraid of the heat: they are summer flowers that they live well in full sun exposure. It tolerates short periods of dryness without damage, but fears excessive humidity: stagnation causes lethal root rot to the plant.
Ground. The land where to grow the sunflower must be draining, preferably rich in organic substance, for this a fertilization before planting, with mature manure or manure. In processing it is necessary dig deep before sowing.
The generic name (Helianthus) comes from two Greek words: "Helios" (= sun) e "Anthos" (= flower) in reference to the tendency of the plant to always turn the bud towards the sun  , before flowering (the mature flower, on the other hand, is always facing east). This behavior is known as heliotropism.
The specific epithet (nodded) indicates the type of biological cycle (annual). Even the common Italian name (Sunflower) recalls the rotation of the buds in the direction of the sun. The term "sunflower" is also used to indicate other plants belonging to the genus "Helianthus", many of which are perennial.
The currently accepted scientific binomial (Helianthus annuus) was proposed by Linnaeus (1707 - 1778) Swedish biologist and writer, considered the father of the modern scientific classification of living organisms, in the publication Species Plantarum of 1753 .
The stem in the countries of origin can exceed 4 m . The biological form of the species is terofita scaposa (T scap), are herbaceous plants that differ from other biological forms because, being annuals, they survive the adverse season in the form of seeds and are also equipped with an erect floral axis, often with few leaves. The plant has a rough pubescence.
The roots are taproot type
The leaves are large in opposite arrangement in the lower part of the stem, and in alternate arrangement in the rest of the plant. The leaves are also long petiolate. The shape is broadly ovate or even triangular and heart-shaped at the base and with a sharp apex. The margins are serrated. The surface is rough and crossed by three nerves. Leaf size: width 5 - 8 cm length 8 - 12 cm. Petiole length: 2 - 20 cm.
What is called the flower is actually the flower head (called inflorescence in general), composed of a set of numerous flowers. The flower head for each plant is generally unique if there are other flower heads (possibly a few, at most up to 9), the lateral ones are smaller. The structure of the flower heads is typical of the Asteraceae: an enlarged peduncle supports a hairy hemispherical envelope composed of several bracts (or scales, generally from 20 to 30) available imbricated and placed in different series that protect the slightly convex and equipped receptacle of straws enveloping the seeds , on which two types of flowers are inserted: the external ones, called "petal flowers" (from 17 to 30), ligulate which can be yellow, or possibly brown, orange or other colors (especially in the cultivars) and the internal ones, called "disc flowers" (up to 150, but even more), are arranged in a single row and are dark orange-brown tubular. The bracts of the envelope are of two types: the external ones of the foliate type, broadly ovate and sharp, the internal ones that are shorter, linear (similar to the spikes of the receptacle) and half embracing the achenes. Flower head diameter: 8 to 15 cm (20 to 50 cm in cultivated plants). Peduncle length: 20 cm. Casing diameter: 15 - 40 mm (maximum 200 mm). Size of the scales / bracts: width 5 - 8 mm length 13 - 25 mm.
The arrangement of the flowers inside the disk takes place according to the golden section, obtaining a spiral pattern in which the number of hourly and anti-clockwise spirals are successive Fibonacci numbers. There are usually 34 spirals in one direction and 55 in the other. In very large sunflowers you can find 89 spirals in one direction and 144 in the other.
The flowers are sympathetic, zygomorphic (the ligulate ones) and actinomorphic (the tubular ones) are also tetra-cyclic (i.e. formed by 4 verticils: calyx - corolla - androecium - gynoecium) and pentamers (calyx and corolla formed by 5 elements). They are also hermaphrodites, more precisely the flowers of the ray (the ligulate ones) are sterile while those of the central disc (tubulosis) are bisexual.
As the disc flowers mature, they become seeds. However, what is commonly called seed is actually the fruit (an achene) of the plant, with the real seeds surrounded by indigestible chaff and provided with a pappus formed by two linear-acute and precociously deciduous scales (or teeth) . The shape of the achenes ranges from oval to oblong and is longitudinally compressed (Amigdaliforme). The color is variable from black to light gray. The surface is velvety. The seeds have different colors and sizes: they are distinguished in short, medium and long (in the medium ones the length is double the width, while the shorter ones contain more oil) the colors range from white, to straw-yellow, to gray and up to blackish . Fruit size: 8 - 15 mm. Length of scales / teeth: 1 - 3.5 mm.
Early stage of the formation of the flower head
The ligules are almost completely open
The ligules have fully opened
From a phytosociological point of view, the species of this item belongs to the following plant community :
Training: of the nitrophilic pioneer therophile communities Class: Chenopodio-Stellarienea mediae
The family to which the H. annuus (Asteraceae or Compositae, nomen conservandum) is the most numerous in the plant world, it includes over 23000 species distributed over 1535 genera  (22750 species and 1530 genera according to other sources ). The gender of belonging (Helianthus) is composed of about 50-70 species according to the various authors. The various species of the genus are distinguished above all on the basis of the biological cycle: annual or multi-year. H. annuus obviously belongs to the first group. The chromosomal number of H. annuus is: 2n = 34  .
H. annuus it is a highly variable species and still lacks a stable and widely adopted infraspecific classification. Different forms are present especially with different colorings in the ray flowers. The classification problems are further accentuated by the fact that this species easily hybridizes with other annual species .
Given the economic importance of the species of this item, several studies have been made on the phenomena of hybridization of H. annuus with other species of the same genus. Some of these studies are reported below. Some research has shown that the species Helianthus anomalus SF Blake (1931) is a hybrid derived from the crossing of H. annuus with Helianthus petiolaris Nuttall (1821)   .
The study conducted by Professor Loren Rieseberg (of the UBC Botanical Garden - University of British Columbia, Vancouver, Canada) showed that the two parent species (H. annuus is H. petiolaris) differ in at least ten genomic rearrangements (three inversions and seven translocations) which affect recombination and increase the possibility of introgression of the hybrid daughter species . Besides H. anomalus the two parent species (H. annuus is H. petiolaris), in the past, have produced two other new species: Helianthus deserticola Heiser (1960) is Helianthus paradoxus Heiser (1958). Normally speciation (creation of new species) is associated with polyploidy, in this case instead there was a "diploid hybridization" as both the parent and daughter species are diploid .
A suitable habitat can favor the restoration of fertility in hybrids (and therefore a push favorable to speciation) without necessarily a modification of the chromosomal number (homoploid hybridization). In the previous case for example H. annuus prefers compact and clayey soils, while H. petiolaris prefers sandy soils. The three hybrids mentioned inhabit completely different substrates: H. anomalus is H. deserticola colonize very arid soils, while H. paradoxus it thrives well in humid and brackish areas . The species of this entry was also useful for studying introgressive (or introgression) hybridization.
This process consists in continuous crossbreeding of the hybrid descendants with one of the parental species, thus obtaining that some characteristics of one species are permanently incorporated into the other (useful for example in cultivation to obtain precise desired characteristics) . Another study was done on natural hybrids of H. annuus with Helianthus argophyllus Torrey & A. Gray (1842). The daughter species differ from each other by two reciprocal chromosomal translocations (a chromosome fragment is transferred to another non-homologous chromosome) thus reducing the fertility of the hybrids .
This entity has had different nomenclatures over time. The following list indicates some of the more frequent synonyms  :
The "Common Sunflower" is one of the most characteristic and recognizable flowers and therefore difficult to confuse with other species. Here the other species of the same genus are briefly mentioned (Helianthus) spontaneously present on the Italian territory . All are however considered sub-spontaneous or naturalized exotic.
Some parts [What parts of the plant and at what stages of its life?] of this flower contain the glucoside of quercetin (quercimeritrina), some amino bases, the calcium salts of solanic acid and a xanthophyll. The healing properties according to folk medicine are  :
It is a melliferous plant and monofloral honey can be obtained in areas of wide cultivation, it has a rapid crystallization and an intense yellow. Sunflower seeds are eaten peeled and roasted, often salted as a snack, especially in China, the United States and Europe. They can be used for salads or an oil can be extracted. Even today there are varieties with a high content of oleic acid that do not differ too much from the composition of olive oil.
Squeezing sunflower seeds contain the following substances :
|water||6 – 14%|
|nitrogenous substances||8 – 19%|
|fatty oil||22 – 36%|
|non-nitrogenous substances||13 – 21%|
|cellulose and ash||25 – 35%|
|Major sunflower seed producers in 2018 |
The seeds are also used as feed for birds and rodents. Engine oil can also be extracted, used to produce biodiesel, cheaper than other fuels. The squeezing residues are used as livestock feed. I girasoli producono del lattice, oggetto di esperimenti volti a utilizzarli come fonti alternative di gomma ipoallergenica.
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Le api hanno bisogno di te, non perderti nemmeno un buzz!
Rosmarino ( Rosmarinus officinalis) . Pianta perenne aromatica, forma un arbusto sempreverde e può essere coltivata sia in giardino che in vaso. In primavera si riempi dei caratteristici fiori che il cui colore spazia dal bianco all’azzurro al lilla.
Tarassaco ( Taraxacum officinale ). Comunemente conosciuto come dente di leone o cicoria selvatica, è una pianta perenne che si trova normalmente nei nostri prati o giardini senza il bisogno di seminarla. Il caratteristico fiore giallo attira le api ed è una delle prime fonti di nutrimento dopo la fine dell’inverno.
Sage ( Salvia officinalis ). È una pianta perenne aromatica molto conosciuta sia per le sue proprietà che per gli svariati usi in cucina. La fioritura avviene tra marzo e maggio e dà vita a fiori dal colore rosa-violaceo.
Trifoglio ( Trifolium ). Presente in numerose varietà, è molto facile da coltivare e viene sempre più spesso scelto perché aiuta a migliorare la fertilità del terreno. È anche utile per le api e fiorisce da aprile a luglio.
Lavanda ( Lavandula angustifolia ). Conosciutissima in tutto il mondo, la lavanda presenta la classica inflorescenza a spiga ed è ricordata per il suo tipico profumo. È molto utile per le api essendo non solo fonte di nettare, ma anche un efficace antifungineo.
Echinacea ( Echinacea ). Comprendente 9 specie di interesse botanico ed erboristico, fiorisce tra giugno e agosto ed è una pianta che si adatta facilmente a diverse condizioni ambientali.
Achillea ( Achillea Millefolium ). È una pianta erbacea perenne molto diffusa nei nostri prati. Sebbene da molti sia considerata una pianta infestante, i suoi fiori sono molto utili per le api.
Girasole ( Helianthus annuus ). Il girasole è molto utile per la raccolta di nettare, da cui si produce un miele molto buono. Tuttavia, probabilmente a causa della diffusione di sementi OGM resistenti a un particolare diserbante usato nella coltivazioni di girasoli, si sono registrati crescenti fenomeno di moria di api. È quindi fondamentale scegliere sementi biologiche e geneticamente non modificate.
Calendula ( Calendula officinalis ). È una pianta rustica che si adatta facilmente alle diverse condizioni ambientali. I suoi caratteristici fiori giallo-arancio attirano gli insetti impollinatori e sono molto conosciuti per le loro proprietà lenitive.
Malva ( Malva sylvestris ). È una pianta erbacea perenne i cui fiori sbocciano da aprile fino ad ottobre e presentano quella caratteristica sfumatura violacea che ne ha preso il nome. Conosciuta per le sue proprietà antiinfiammatorie ed emollienti, è anche una ricca riserva di nettare per le api.
Tagete ( Tagetes ). Pianta originaria del continente americano, è conosciuta per i bellissimi fiori il cui colore va da giallo all’arancio fino al rosso intenso. Usati in svariate culture per scopi rituali, i fiori attirano anche le api per le loro riserve nettarifere.