Helianthus or sunflower (/ˌhiːliˈænθəs/) is a genus of plants comprising about 70 species. Except for three species in South America, all Helianthus species are native to North America. The common name, "sunflower", typically refers to the popular annual species Helianthus annuus, or the common sunflower, whose round flower heads in combination with the ligules look like the sun. This and other species, notably Jerusalem artichoke (H. tuberosus), are cultivated in temperate regions and some tropical regions as food crops for humans, cattle, and poultry, and as ornamental plants. The species H. annuus typically grows during the summer and into early fall, with the peak growth season being mid-summer.
Perennial sunflower species are not as common in garden use due to their tendency to spread rapidly and become invasive. The whorled sunflower, Helianthus verticillatus, was listed as an endangered species in 2014 when the U.S. Fish and Wildlife Service issued a final rule protecting it under the Endangered Species Act. The primary threats are industrial forestry and pine plantations in Alabama, Georgia, and Tennessee. They grow to 1.8 m (6 ft) and are primarily found in woodlands, adjacent to creeks and moist, prairie-like areas.
Temporal range: Eocene-recent
Harpalium (Cass.) Cass.
Sunflowers are usually tall annual or perennial plants that in some species can grow to a height of 300 cm (120 in) or more. They bear one or more wide, terminal capitula (flower heads), with bright yellow ray florets at the outside and yellow or maroon (also known as a brown/red) disc florets inside. Several ornamental cultivars of H. annuus have red-colored ray florets; all of them stem from a single original mutant. During growth, sunflowers tilt during the day to face the sun but stop once they begin blooming. This tracking of the sun in young sunflower heads is called heliotropism. By the time they are mature, sunflowers generally face east. The rough and hairy stem is branched in the upper part in wild plants but is usually unbranched in domesticated cultivars. The petiolate leaves are dentate and often sticky. The lower leaves are opposite, ovate, or often heart-shaped.
They are distinguished technically by the fact that the ray florets (when present) are sterile, and by the presence on the disk flowers of a pappus that is of two awn-like scales that are caducous (that is, easily detached and falling at maturity). Some species also have additional shorter scales in the pappus, and one species lacks a pappus entirely. Another technical feature that distinguishes the genus more reliably, but requires a microscope to see, is the presence of a prominent, multicellular appendage at the apex of the style. Further, the florets of a sunflower are arranged in a natural spiral.
Variability is seen among the perennial species that make up the bulk of those in the genus. Some have most or all of the large leaves in a rosette at the base of the plant and produce a flowering stem that has leaves that are reduced in size. Most of the perennials have disk flowers that are entirely yellow, but a few have disk flowers with reddish lobes. One species, H. radula, lacks ray flowers altogether.
The growth of a sunflower strictly depends on its genetic makeup and background. Additionally, the season it is planted will have effects on its development. Sunflower development is classified by a series of vegetative stages and reproductive stages that can be determined by identifying the heads or main branch of a single head or branched head. 
The Journal of Environmental Management has analyzed the impact of various nitrogen-based fertilizers on the growth of sunflowers. Ammonium nitrate was found to produce better nitrogen absorption than urea, which performed better in low-temperature areas.
In Brazil, a unique system of production called the soybean-sunflower system is used: sunflowers are planted first, and then soybean crops follow, reducing idle periods and increasing total sunflower production and profitability. Sunflowers are usually planted in the extreme southern or northern regions of the country. Frequently, in the southern regions, sunflowers are grown in the beginning of rainy seasons, and soybeans can then be planted in the summer. Researchers have concluded that the soybean-sunflower method of plantation could be further improved through changes in fertilizer use. The current method has been shown to have positive environmental impacts.
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Bubble-tip anemone (Entacmaea quadricolor) is a species of sea anemone in the family Actiniidae. Like several anemone species, E. quadricolor can support several anemonefish species, and displays two growth types based on where they live in the water column, one of which gives it the common name, due to the bulbous tips on its tentacles.Heliantheae
The Heliantheae (sometimes called the sunflower tribe) are the third-largest tribe in the sunflower family (Asteraceae). With some 190 genera and nearly 2500 recognized species, only the tribes Senecioneae and Astereae are larger. The name is derived from the genus Helianthus, which is Greek for sun flower. Most genera and species are found in North America and South America, particularly in Mexico. A few genera are pantropical.
Most Heliantheae are herbs or shrubs, but some grow to the size of small trees. Leaves are usually hairy and arranged in opposite pairs. The anthers are usually blackened.
The above statements about the size and distribution of the tribe apply to a broad definition of Heliantheae, which was followed throughout the 20th century. Some recent authors break the tribe up into a dozen or so smaller tribes.Helianthus annuus
Helianthus annuus, the common sunflower, is a large annual forb of the genus Helianthus grown as a crop for its edible oil and edible fruits. This sunflower species is also used as wild bird food, as livestock forage (as a meal or a silage plant), in some industrial applications, and as an ornamental in domestic gardens. The plant was first domesticated in the Americas. Wild Helianthus annuus is a widely branched annual plant with many flower heads. The domestic sunflower, however, often possesses only a single large inflorescence (flower head) atop an unbranched stem. The name sunflower may derive from the flower's head's shape, which resembles the sun, or from the impression that the blooming plant appears to slowly turn its flower towards the sun as the latter moves across the sky on a daily basis.
Sunflower seeds were brought to Europe from the Americas in the 16th century, where, along with sunflower oil, they became a widespread cooking ingredient.Helianthus bolanderi
Helianthus bolanderi is a species of sunflower known by the common names Bolander's sunflower and serpentine sunflower. It is native to California and Oregon, where it grows mainly in mountainous areas, often in serpentine soils. It has been found from southwestern Oregon as well as in northern and central California as far south as Santa Cruz County, with reports of a few isolated populations in southern California (some of them from urban areas and very likely cultivated or escaped specimens).This wild sunflower is an erect annual reaching heights over a meter (40 inches). It has a hairy, rough stem with leaves lance- or oval-shaped, usually pointed, sometimes serrated along the edges, and 3 to 15 centimeters (1.2-6.0 inches) long. The inflorescence holds one or more flower heads, and each plant may have many inflorescences growing along the full length of the stem. The flower head has a cup of long, pointed phyllaries holding an array of bright yellow ray florets each one to two centimeters (0.4-0.8 inches) long around a center of yellow to dark purple or reddish disc florets. The achene is 3 to 5 millimeters (0.12-0.20 inches) long.Helianthus divaricatus
Helianthus divaricatus, commonly known as the rough sunflower, woodland sunflower or rough woodland sunflower, is a North American species perennial herb in the composite family. It is native to central and eastern North America, from Ontario and Quebec in the north, south to Florida and Louisiana and west to Oklahoma and Iowa.Helanthus divaricatus commonly occurs in dry, relatively open sites. The showy yellow flowers emerge in summer through early fall.The woodland sunflower is similar to Helianthus hirsutus, but its stem is rough. It is up to 1.5 m tall with short stalked, lanceolate to oval leaves, 1–8 cm wide with toothed margins. Its flowers have 8 to 15 rays, each 1.5 to 3 cm (0.6-1.2inches) long, surrounding an orange or yellowish brown central disk.Helianthus giganteus
Helianthus giganteus (giant sunflower or tall sunflower), is a species of Helianthus native to the eastern United States and eastern and central Canada, from Newfoundland west to Alberta south to Minnesota, Mississippi, and South Carolina.Helianthus giganteus is a perennial herbaceous plant growing up to 4 m (over 13 feet) tall. The leaves are slender, lanceolate. The flower heads are bright yellow, up to 7 cm (2.8 inches) in diameter. They are most commonly found in valleys with wet meadows or swamps.Helianthus hirsutus
Helianthus hirsutus is a North American species of sunflower known by the common name hairy sunflower. It is widespread across south-central Canada, the eastern and central United States, and northeastern Mexico. It ranges from Ontario south to Florida, Coahuila, and Nuevo León, and west as far as Minnesota, Nebraska, and Texas.Helianthus hirsutus is a perennial sometimes as much as 200 cm (almost 7 feet) tall, spreading by means of underground rhizomes. Leaves and stems are covered with stiff hairs. One plant can produce 1-7 flower heads, each with 10–15 yellow ray florets surrounding 40 or more yellow disc florets. The species grows in sunny locations in open forests or along the edges of forests.Helianthus maximiliani
Helianthus maximiliani is a North American species of sunflower known by the common name Maximilian sunflower.This sunflower is named for Prince Maximilian of Wied-Neuwied, who encountered it on his travels in North America.
Helianthus maximiliani is native to the Great Plains in central North America, and naturalized in the eastern and western parts of the continent. It is now found from British Columbia to Maine, south to the Carolinas, Chihuahua, and California. The plant thrives in a number of ecosystems, particularly across the plains in central Canada and the United States. It is also cultivated as an ornamental.Helianthus nuttallii
Helianthus nuttallii (Nuttall's sunflower) is a species of sunflower native to northern, central, and western North America, from Newfoundland west to British Columbia, south to Missouri, New Mexico, and California.Helianthus nuttallii is a herbaceous perennial plant growing to 50–400 cm (20-160 inches) tall. The leaves are opposite on the lower part of the stem, alternate higher up, narrow lanceolate, 8–20 cm (3.2-8.0 inches) long and 6–30 mm wide, with a rough texture. The flowers are yellow, produced in a flowerhead approximately 9 cm (3.6 inches) diameter with 10–20 ray florets and at least 60 disc florets; each stem bears one to a few flowerheads.
SubspeciesHelianthus nuttallii subsp. nuttallii - Canada, western United States. H. nuttallii subsp. nuttallii is considered by some to be a synonym for H. nuttallii. However, others argue that it is distinct from the species.
Helianthus nuttallii subsp. parishii (A.Gray) Heiser - (Los Angeles sunflower). Southern California, endemic. It is an endangered subspecies thought to have been extinct since 1937, but it was rediscovered in southern California in 2001.
Helianthus nuttallii subsp. rydbergii (Britton) R. Long. - Central Canada, interior northwestern United StatesHelianthus occidentalis
Helianthus occidentalis (fewleaf sunflower or western sunflower) is a species of sunflower native to the Eastern and Central United States. It grows mostly in the Great Lakes Region and in the Ozarks, with additional populations scattered as far as Massachusetts, Texas, and the Florida Panhandle.H. occidentalis differs from other, similar species by its sparse leaves, most of which are crowded around the lower part of the stem. This perennial plant reaches heights from 2 to 5 ft (60–150 cm). It produces one to several yellow flower heads, each with 8-14 ray florets surrounding more than 50 disc florets.The word occidentalis means "western" in Latin. The plant was first described in 1836, when the Great Lakes Region was considered the western part of the United States.
SubspeciesH. o. subsp. occidentalis - most of species range
H. o. subsp. plantagineus (Torr. & A.Gray) Shinners - Texas, ArkansasHelianthus pauciflorus
Helianthus pauciflorus, called the stiff sunflower, is a North American plant species in the sunflower family. It is widespread across the Great Plains, the Rocky Mountains, and the Great Lakes region, and naturalized in scattered locations in the eastern United States and in much of southern Canada (from Alberta to Nova Scotia).Stiff sunflower is a perennial herb 50–200 cm (1 ft 8 in–6 ft 7 in) tall, spreading by means of underground rhizomes. Most of the leaves are attached near the bottom of the stem. One plant can produces 1-10 flower heads, each head with 10-20 yellow ray florets surrounding at least 75 red or (less often) yellow disc florets.Hybrids between H. pauciflorus and H. tuberosus (Jerusalem artichoke) are known as H. × laetiflorus. The name H. laetiflorus has also been used as a synonym of H. pauciflorus.
SubspeciesHelianthus pauciflorus subsp. pauciflorus: 80–200 cm (2 ft 7 in–6 ft 7 in) tall; leaves alternate near the end of the stem, 8–27 cm (3 1⁄4–10 3⁄4 in) long, with tips acuminate (tapered to a point).
Helianthus pauciflorus subsp. subrhomboideus (Rydb.) O.Spring & E.E.Schill.: 50–120 cm (1 ft 8 in–3 ft 11 in) tall; leaves opposite, 5–12 cm (2–5 in) long, with acute or obtuse tips.Helianthus petiolaris
Helianthus petiolaris is a North American plant species in the sunflower family, commonly known as the prairie sunflower or lesser sunflower. Naturalist and botanist Thomas Nuttall was the first to describe the prairie sunflower in 1821. The word petiolaris in Latin means, “having a petiole”. The species originated in Western United States, but has since expanded east. The prairie sunflower is sometimes considered a weed.Helianthus strumosus
Helianthus strumosus, the paleleaf woodland sunflower, is a species of sunflower native to North America east of the Great Plains.Helianthus × laetiflorus
Helianthus × laetiflorus, the cheerful sunflower or perennial sunflower, is a plant in the daisy family, Asteraceae. It is widespread in scattered locations across much of Canada from Newfoundland to British Columbia, and the central and eastern United States as far south as Texas and Georgia.Jerusalem artichoke
The Jerusalem artichoke (Helianthus tuberosus), also called sunroot, sunchoke, or earth apple, is a species of sunflower native to central North America. It grows wild in eastern and western North America but is considered an introduced species. It is also cultivated widely across the temperate zone for its tuber, which is used as a root vegetable.Rudbeckia hirta
Rudbeckia hirta, commonly called black-eyed Susan, is a North American flowering plant in the sunflower family, native to Eastern and Central North America and naturalized in the Western part of the continent as well as in China. It has now been found in all 10 Canadian Provinces and all 48 of the states in the contiguous United States.Rudbeckia hirta is one of a number of plants with the common name black-eyed Susan. Other common names for this plant include: brown-eyed Susan, brown betty, gloriosa daisy, golden Jerusalem, English bull's eye, poor-land daisy, yellow daisy, and yellow ox-eye daisy.Rudbeckia hirta is the state flower of Maryland.The plant also is a traditional Native American medicinal herb in several tribal nations; believed in those cultures to be a remedy, among other things, for colds, flu, infection, swelling and (topically, by poultice) for snake bite (although not all parts of the plant are edible)Parts of the plant have nutritional value. Other parts are not edible.Stichodactyla helianthus
Stichodactyla helianthus, commonly known as sun anemone, is a sea anemone of the family Stichodactylidae. Helianthus stems from the Greek words ἡλιος (meaning sun), and ἀνθος, meaning flower. S. helianthus is a large, green, sessile, carpet-like sea anemone, from the Caribbean. It lives in shallow areas with mild to strong currents. The anemone crab (Mithraculus cinctimanus) is often associated with it, being found among the tentacles or on the column and margin of the oral disc, as is the sun anemone shrimp.
S. helianthus excretes stichodactyla toxin. It is believed that it excretes toxins mainly to protect itself from the spiny lobster.Sunflower oil
Sunflower oil is the non-volatile oil pressed from the seeds of sunflower (Helianthus annuus). Sunflower oil is commonly used in food as a frying oil, and in cosmetic formulations as an emollient. The world's total production of sunflower oil in 2014 was nearly 16 million tonnes, with Ukraine and Russia as the largest producers.Sunflower oil is a mixture mainly of the polyunsaturated fat, linoleic acid (59% of total), and the monounsaturated fat, oleic acid (30% of total). In sunflower oil plant breeding and manufacturing, four types of processed oil containing different amounts of the major fatty acids are produced. The expressed oil has light amber color with a mild flavor. The oil contains a rich content of vitamin E.
As of 2017, genome analysis and development of hybrid sunflowers to increase oil production are under development to meet greater consumer demand for sunflower oil and its commercial varieties.USS Helianthus (SP-585)
USS Helianthus (SP-585) was a patrol vessel in commission in the United States Navy from 1917 to 1919, seeing service in World War I. After her U.S. Navy service, she was in commission in the United States Coast and Geodetic Survey as the survey launch USC&GS Helianthus from 1919 to 1939. She was named after the Helianthus, the genus to which the sunflower belongs.