Chrysanthemums (//), sometimes called mums or chrysanths, are flowering plants of the genus Chrysanthemum in the family Asteraceae. They are native to East Asia and northeastern Europe. Most species originate from East Asia and the center of diversity is in China. Countless horticultural varieties and cultivars exist.
The genus Chrysanthemum are perennial herbaceous flowering plants, sometimes subshrubs. The leaves are alternate, divided into leaflets and may be pinnatisect, lobed, or serrate (toothed) but rarely entire. The compound inflorescence is an array of several flower heads, or sometimes a solitary head. The head has a base covered in layers of phyllaries. The simple row of ray florets is white, yellow, or red. The disc florets are yellow. Pollen grains are approximately 34 microns. The fruit is a ribbed achene. 
The genus Chrysanthemum was first formally described by Linnaeus in 1753, with 14 species, and hence bears his name (L.) as the botanical authority. The genus once included more species, but was split several decades ago[when?] into several genera, putting the economically important florist's chrysanthemums in the genus Dendranthema. The naming of these genera has been contentious, but a ruling of the International Botanical Congress in 1999 changed the defining species of the genus to Chrysanthemum indicum, restoring the florist's chrysanthemums to the genus Chrysanthemum.
Genera now separated from Chrysanthemum include Argyranthemum, Glebionis, Leucanthemopsis, Leucanthemum, Rhodanthemum, and Tanacetum.
As of February 2020[update], Plants of the World Online accepted the following species:
Former species include:
The name "chrysanthemum" is derived from the Ancient Greek: χρυσός chrysos (gold) and Ancient Greek: ἄνθεμον anthemon (flower).
Chrysanthemums start blooming in early autumn. This is also known as the favorite flower for the month of November.
Chrysanthemums (Chinese: 菊花; pinyin: Júhuā) were first cultivated in China as a flowering herb as far back as the 15th century BC. Over 500 cultivars had been recorded by 1630. By 2014 it was estimated that there were over 20,000 cultivars in the world and about 7,000 cultivars in China. The plant is renowned as one of the Four Gentlemen (四君子) in Chinese and East Asian Art. The plant is particularly significant during the Double Ninth Festival.
Chrysanthemum cultivation began in Japan during the Nara and Heian periods (early 8th to late 12th centuries), and gained popularity in the Edo period (early 17th to late 19th century). Many flower shapes, colours, and varieties were created. The way the flowers were grown and shaped also developed, and chrysanthemum culture flourished. Various cultivars of chrysanthemums created in the Edo period were characterized by a remarkable variety of flower shapes, and were exported to China from the end of the Edo period, changing the way Chinese chrysanthemum cultivars were grown and their popularity. In addition, from the Meiji period (late 19th to early 20th century), many cultivars with flowers over 20 cm (7.87 in) in diameter, called the Ogiku (lit., great chrysanthemum) style were created, which influenced the subsequent trend of chrysanthemums. The Imperial Seal of Japan is a chrysanthemum and the institution of the monarchy is also called the Chrysanthemum Throne. A number of festivals and shows take place throughout Japan in autumn when the flowers bloom. Chrysanthemum Day (菊の節句, Kiku no Sekku) is one of the five ancient sacred festivals. It is celebrated on the 9th day of the 9th month. It was started in 910, when the imperial court held its first chrysanthemum show.
Chrysanthemums entered American horticulture in 1798 when Colonel John Stevens imported a cultivated variety known as 'Dark Purple' from England. The introduction was part of an effort to grow attractions within Elysian Fields in Hoboken, New Jersey.
Modern cultivated chrysanthemums are showier than their wild relatives. Many horticultural specimens have been bred to bear many rows of ray florets in a great variety of colors. The flower heads occur in various forms, and can be daisy-like or decorative, like pompons or buttons. This genus contains many hybrids and thousands of cultivars developed for horticultural purposes. In addition to the traditional yellow, other colors are available, such as white, purple, and red. The most important hybrid is Chrysanthemum × morifolium (syn. C. × grandiflorum), derived primarily from C. indicum, but also involving other species.
Over 140 cultivars of chrysanthemum have gained the Royal Horticultural Society's Award of Garden Merit (confirmed 2017).
Chrysanthemums are divided into two basic groups, garden hardy and exhibition. Garden hardy chrysanthemums are perennials capable of wintering in most northern latitudes. Exhibition varieties are not usually as sturdy. Garden hardy varieties are defined by their ability to produce an abundance of small blooms with little if any mechanical assistance, such as staking, and withstanding wind and rain. Exhibition varieties, though, require staking, overwintering in a relatively dry, cool environment, and sometimes the addition of night lights.
The exhibition varieties can be used to create many amazing plant forms, such as large disbudded blooms, spray forms, and many artistically trained forms, such as thousand-bloom, standard (trees), fans, hanging baskets, topiary, bonsai, and cascades.
Chrysanthemum blooms are divided into 13 different bloom forms by the US National Chrysanthemum Society, Inc., which is in keeping with the international classification system. The bloom forms are defined by the way in which the ray and disk florets are arranged. Chrysanthemum blooms are composed of many individual flowers (florets), each one capable of producing a seed. The disk florets are in the center of the bloom head, and the ray florets are on the perimeter. The ray florets are considered imperfect flowers, as they only possess the female reproductive organs, while the disk florets are considered perfect flowers, as they possess both male and female reproductive organs.
Irregular incurves are bred to produce a giant head called an ogiku. The disk florets are concealed in layers of curving ray florets that hang down to create a 'skirt'. Regular incurves are similar, but usually with smaller blooms and a dense, globular form. Intermediate incurve blooms may have broader florets and a less densely flowered head.
In the reflex form, the disk florets are concealed and the ray florets reflex outwards to create a mop-like appearance. The decorative form is similar to reflex blooms, but the ray florets usually do not radiate at more than a 90° angle to the stem.
The pompon form is fully double, of small size, and very globular in form. Single and semidouble blooms have exposed disk florets and one to seven rows of ray florets. In the anemone form, the disk florets are prominent, often raised and overshadowing the ray florets. The spoon-form disk florets are visible and the long, tubular ray florets are spatulate. In the spider form, the disk florets are concealed, and the ray florets are tube-like with hooked or barbed ends, hanging loosely around the stem. In the brush and thistle variety, the disk florets may be visible.
In Japan, a form of bonsai chrysanthemum was developed over the centuries. The cultivated flower has a lifespan of about 5 years and can be kept in miniature size. Another method is to use pieces of dead wood and the flower grows over the back along the wood to give the illusion from the front that the miniature tree blooms.
Yellow or white chrysanthemum flowers of the species C. morifolium are boiled to make a tea in some parts of East Asia. The resulting beverage is known simply as chrysanthemum tea (菊 花 茶, pinyin: júhuā chá, in Chinese). In Korea, a rice wine flavored with chrysanthemum flowers is called gukhwaju (국화주).
Chrysanthemum leaves are steamed or boiled and used as greens, especially in Chinese cuisine. The flowers may be added to dishes such as mixian in broth, or thick snakemeat soup (蛇羹) to enhance the aroma. Japanese cuisine sashimi uses small chrysanthemums as garnish.
Pyrethrum (Chrysanthemum [or Tanacetum] cinerariaefolium) is economically important as a natural source of insecticide. The flowers are pulverized, and the active components, called pyrethrins, which occur in the achenes, are extracted and sold in the form of an oleoresin. This is applied as a suspension in water or oil, or as a powder. Pyrethrins attack the nervous systems of all insects, and inhibit female mosquitoes from biting. In sublethal doses, they have an insect-repellent effect. They are harmful to fish, but are far less toxic to mammals and birds than many synthetic insecticides. They are not persistent, being biodegradable, and also decompose easily on exposure to light. Pyrethroids such as permethrin are synthetic insecticides based on natural pyrethrum. Despite this, chrysanthemum leaves are still a major host for destructive pests, such as leafminer flies including L. trifolii.
Persian powder is an example of industrial product of chrysanthemum insecticide.
Chrysanthemum plants have been shown to reduce indoor air pollution by the NASA Clean Air Study.
In some European countries (e.g., France, Belgium, Italy, Spain, Poland, Hungary, Croatia), incurve chrysanthemums symbolize death and are used only for funerals or on graves, while other types carry no such symbolism; similarly, in China, Japan, and Korea of East Asia, white chrysanthemums symbolize adversity, lamentation, and/or grief. In some other countries, they represent honesty. In the United States, the flower is usually regarded as positive and cheerful, with New Orleans as a notable exception.
In the Victorian language of flowers, the chrysanthemum had several meanings. The Chinese chrysanthemum meant cheerfulness, whereas the red chrysanthemum stood for "I Love", while the yellow chrysanthemum symbolized slighted love. The chrysanthemum is also the flower of November.
Chrysanthemums first arrived in Japan by way of China in the 5th century. The chrysanthemum has been used as a theme of waka (Japanese traditional poetry) since around the 10th century in the Heian period, and Kokin Wakashū is the most famous of them. In the 12th century, during the Kamakura period, when the Retired Emperor Go-Toba adopted it as the mon (family crest) of the Imperial family, it became a flower that symbolized autumn in Japan. During the Edo period from the 17th century to the 19th century, due to the development of economy and culture, the cultivation of chrysanthemums, cherry blossoms, Japanese iris, morning glory, etc. became popular, many cultivars were created and many chrysanthemum exhibitions were held. From the Meiji period in the latter half of the 19th century, due to the growing importance of the chrysanthemum, which symbolized the Imperial family, the creation of ogiku style cultivars with a diameter of 20 cm or more became popular.
In the present day, each autumn there are chrysanthemum exhibitions at the Shinjuku Gyo-en, Meiji Shrine and Yasukuni Shrine in Tokyo. The Yasukuni Shrine, formerly a state-endowed shrine (官国弊社, kankokuheisha) has adopted the chrysanthemum crest. Culinary-grade chrysanthemums are used to decorate food, and they remain a common motif for traditional Japanese arts like porcelain, lacquerware and kimono.
Chrysanthemum growing is still practised actively as a hobby by many Japanese people who enter prize plants in contests. Chrysanthemum "dolls", often depicting fictional characters from both traditional sources like kabuki and contemporary sources like Disney, are displayed throughout the fall months, and the city of Nihonmatsu hosts the "Nihonmatsu Chrysanthemum Dolls Exhibition" every autumn in historical ruin of Nihonmatsu Castle. They are also grown into chrysanthemum bonsai forms.
Korea has a number of flower shows that exhibit the chrysanthemum, such as the Masan Gagopa Chrysanthemum Festival.
In Iran, chrysanthemums are associated with the Zoroastrian spiritual being Ashi Vanghuhi (lit. 'good blessings, rewards'), a female Yazad (angel) presiding over blessings.
In 2017, Israel named a new fast-growing Chrysanthemum flower after Narendra Modi, the Prime Minister of India, in a special gesture to mark the first visit of an Indian prime minister to the Jewish nation.
In Australia, on Mother's Day, which falls in May when the flower is in season, people traditionally wear a white chrysanthemum, or a similar white flower to honour their mothers. Chrysanthemums are often given as Mother's Day presents.
Italian composer Giacomo Puccini wrote Crisantemi (1890), a movement for string quartet, in memory of his friend Amedeo di Savoia Duca d'Aosta. In Italy (and other European countries) the chrysanthemum is the flower that people traditionally bring to their deceased loved ones at the cemetery and is generally associated with mourning. A probable reason for this is the fact that the plant flowers between the end of October and the beginning of November, coinciding with the Day of the Dead (2 November).
Chrysanthemums are placed on graves to honor the dead during All Saints' Day and All Souls' Day in Poland.
The UK National Collection of hardy chrysanthemums is at Hill Close Gardens near Warwick.