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Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of with blooms that are often colourful and fragrant. Orchids are cosmopolitan plants that are found in almost every habitat on Earth except . The world's richest diversity of orchid genera and species is found in the .

Orchidaceae is one of the two largest families of flowering plants, along with the . It contains about 28,000 currently accepted distributed across 763 . (See External links below).

The Orchidaceae family encompasses about 6–11% of all species of . The largest genera are (2,000 species), (1,500 species), (1,400 species) and (1,000 species). It also includes Vanilla (the genus of the vanilla plant), the type genus , and many commonly cultivated plants such as and . Moreover, since the introduction of tropical species into cultivation in the 19th century, have produced more than 100,000 hybrids and .


Description
Orchids are easily distinguished from other plants, as they share some very evident derived characteristics or . Among these are: bilateral symmetry of the flower (), many resupinate flowers, a nearly always highly modified (labellum), fused and , and extremely small .


Stem and roots
All orchids are that lack any permanent structure. They can grow according to two patterns:
  • : The stem grows from a single bud, leaves are added from the apex each year, and the stem grows longer accordingly. The stem of orchids with a monopodial growth can reach several metres in length, as in and Vanilla.
  • : Sympodial orchids have a front (the newest growth) and a back (the oldest growth).Nash, N., and Frownie, S. (2008). Complete guide to orchids. (Meredith Publishing Group) p. 12. The plant produces a series of adjacent shoots, which grow to a certain size, bloom and then stop growing and are replaced. Sympodial orchids grow horizontally, rather than vertically, following the surface of their support. The growth continues by development of new leads, with their own leaves and roots, sprouting from or next to those of the previous year, as in . While a new lead is developing, the may start its growth again from a so-called 'eye', an undeveloped bud, thereby branching. Sympodial orchids may have visible joined by a , which creeps along the top or just beneath the soil.

'', collected in ; the small size, compared to a one-Euro coin, and the two globose tuberoids typical of the genus are highlighted]]

Terrestrial orchids may be or form or . The root caps of terrestrial orchids are smooth and white.

Some sympodial terrestrial orchids, such as and , have two subterranean . One is used as a food reserve for wintry periods, and provides for the development of the other one, from which visible growth develops.

In warm and constantly humid climates, many terrestrial orchids do not need pseudobulbs.

orchids, those that grow upon a support, have modified that can sometimes be a few meters long. In the older parts of the roots, a modified spongy epidermis, called a , has the function of absorbing humidity. It is made of dead cells and can have a silvery-grey, white or brown appearance. In some orchids, the velamen includes spongy and fibrous bodies near the passage cells, called tilosomes.

The cells of the root epidermis grow at a right angle to the axis of the root to allow them to get a firm grasp on their support. Nutrients for epiphytic orchids mainly come from mineral dust, organic detritus, animal droppings and other substances collecting among on their supporting surfaces.

The base of the stem of sympodial epiphytes, or in some species essentially the entire stem, may be thickened to form a that contains nutrients and water for drier periods.

The pseudobulb typically has a smooth surface with lengthwise grooves, and can have different shapes, often conical or oblong. Its size is very variable; in some small species of , it is no longer than two millimeters, while in the largest orchid in the world, Grammatophyllum speciosum (giant orchid), it can reach three meters. Some species have long, canelike pseudobulbs with short, rounded leaves over the whole length; some other orchids have hidden or extremely small pseudobulbs, completely included inside the leaves.

With ageing the pseudobulb sheds its leaves and becomes dormant. At this stage it is often called a backbulb. Backbulbs still hold nutrition for the plant, but then a pseudobulb usually takes over, exploiting the last reserves accumulated in the backbulb, which eventually dies off, too. A pseudobulb typically lives for about five years. Orchids without noticeable pseudobulbs are also said to have growths, an individual component of a sympodial plant.


Leaves
Like most , orchids generally have simple with parallel veins, although some have reticulate . Leaves may be ovate, lanceolate, or orbiculate, and very variable in size on the individual plant. Their characteristics are often diagnostic. They are normally on the stem, often folded lengthwise along the centre ("plicate"), and have no . Orchid leaves often have bodies called stegmata in the sheaths (not present in the ) and are fibrous.

The structure of the leaves corresponds to the specific habitat of the plant. Species that typically bask in sunlight, or grow on sites which can be occasionally very dry, have thick, leathery leaves and the are covered by a waxy to retain their necessary water supply. Shade-loving species, on the other hand, have long, thin leaves.

The leaves of most orchids are perennial, that is, they live for several years, while others, especially those with plicate leaves as in , shed them annually and develop new leaves together with new pseudobulbs.

The leaves of some orchids are considered ornamental. The leaves of Macodes sanderiana, a semiterrestrial or rock-hugging ("") orchid, show a sparkling silver and gold veining on a light green background. The cordate leaves of are light brownish-green with maroon-puce markings, created by flower pigments. The attractive mottle of the leaves of lady's slippers from tropical and subtropical Asia ( ), is caused by uneven distribution of chlorophyll. Also, Phalaenopsis schilleriana is a pastel pink orchid with leaves spotted dark green and light green. The jewel orchid ( ) is grown more for its colorful leaves than its white flowers.

Some orchids, such as Dendrophylax lindenii (ghost orchid), and depend on their green roots for and lack normally developed leaves, as do all of the species.

Orchids of the genus (coralroot orchids) lack leaves altogether and instead wrap their roots around the roots of mature trees and use specialized fungi to harvest sugars.


Flowers
Orchid flowers have three , three petals and a three-chambered ovary. The three sepals and two of the petals are often similar to each other but one petal is usually highly modified, forming a "lip" or labellum. In most orchid genera, as the flower develops, it undergoes a twisting through 180°, called , so that the labellum lies below the column. The labellum functions to attract insects, and in resupinate flowers, also acts as a landing stage, or sometimes a trap.
(2011). 9780646562322, Noel Hoffman.
(2024). 9780980348149, Simon Nevill Publications.

The reproductive parts of an orchid flower are unique in that the and style are joined to form a single structure, the column. Instead of being released singly, thousands of grains are contained in one or two bundles called that are attached to a sticky disc near the top of the column. Just below the pollinia is a second, larger sticky plate called the stigma.


Reproduction

Pollination
The complex mechanisms that orchids have evolved to achieve were investigated by and described in Fertilisation of Orchids (1862). Orchids have developed highly specialized systems, thus the chances of being pollinated are often scarce, so orchid flowers usually remain receptive for very long periods, rendering unpollinated flowers long-lasting in cultivation. Most orchids deliver pollen in a single mass. Each time pollination succeeds, thousands of ovules can be fertilized.

Pollinators are often visually attracted by the shape and colours of the labellum. However, some species attract male fruit flies ( and spp.) solely via a floral chemical which simultaneously acts as a floral reward (e.g. , raspberry , or ) to perform pollination., 28:1161-1172 and 31(3): 509-519. The flowers may produce attractive odours. Although absent in most species, may be produced in a spur of the labellum ( 8 in the illustration above), or on the point of the sepals, or in the septa of the ovary, the most typical position amongst the .

In orchids that produce pollinia, pollination happens as some variant of the following sequence: when the pollinator enters into the flower, it touches a viscidium, which promptly sticks to its body, generally on the head or abdomen. While leaving the flower, it pulls the pollinium out of the anther, as it is connected to the viscidium by the caudicle or stipe. The caudicle then bends and the pollinium is moved forwards and downwards. When the pollinator enters another flower of the same species, the pollinium has taken such position that it will stick to the stigma of the second flower, just below the rostellum, pollinating it. In horticulture, is achieved by removing the pollinia with a small instrument such as a toothpick from the pollen parent and transferring them to the seed parent.

Some orchids mainly or totally rely on , especially in colder regions where pollinators are particularly rare. The caudicles may dry up if the flower has not been visited by any pollinator, and the pollinia then fall directly on the stigma. Otherwise, the anther may rotate and then enter the stigma cavity of the flower (as in Holcoglossum amesianum).

The slipper orchid Paphiopedilum parishii reproduces by . This occurs when the anther changes from a solid to a liquid state and directly contacts the stigma surface without the aid of any pollinating agent or floral assembly.

The labellum of the is , and has the function of trapping visiting insects. The only exit leads to the anthers that deposit pollen on the visitor.

In some extremely specialized orchids, such as the Eurasian genus , the labellum is adapted to have a colour, shape, and odour which attracts male insects via of a receptive female. Pollination happens as the insect attempts to mate with flowers.

Many neotropical orchids are pollinated by male , which visit the flowers to gather volatile chemicals they require to synthesize attractants. Males of such species as Euglossa imperialis or have been observed to leave their territories periodically to forage for aromatic compounds, such as cineole, to synthesize pheromone for attracting and mating with females. Each type of orchid places the pollinia on a different body part of a different species of bee, so as to enforce proper cross-pollination.

A rare orchid growing entirely underground in Australia, Rhizanthella slateri, is never exposed to light, and depends on and other terrestrial insects to pollinate it.

, a genus discussed briefly by , actually launches its viscid pollinia with explosive force when an insect touches a , knocking the pollinator off the flower.

After pollination, the sepals and petals fade and wilt, but they usually remain attached to the ovary.

In 2011, Bulbophyllum nocturnum was discovered to flower nocturnally.


Asexual reproduction
Some species, such as in the genera Phalaenopsis, Dendrobium, and Vanda, produce offshoots or plantlets formed from one of the nodes along the , through the accumulation of growth hormones at that point. These shoots are known as .Matthew Blanchard, Roberto Lopez, Erik Runkle, PhD, and Yin-Tung Wang, PhD "Growing the Best Phalaenopsis", WWW.AOS.ORG ORCHIDS APRIL 2007

Epipogium aphyllum exhibits a dual reproductive strategy, engaging in both sexual and asexual seed production. The likelihood of playing a substantial role in successful reproduction appears minimal. Within certain petite orchid species groups, there is a noteworthy preparation of female gametes for fertilization preceding the act of pollination.


Fruits and seeds
The ovary typically develops into a capsule that is by three or six longitudinal slits, while remaining closed at both ends.

The are generally almost microscopic and very numerous, in some species over a million per capsule. After ripening, they blow off like dust particles or spores. Most orchid species lack in their seed and must enter symbiotic relationships with various mycorrhizal that provide them the necessary nutrients to germinate, so almost all orchid species are mycoheterotrophic during germination and reliant upon fungi to complete their lifecycles. Only a handful of orchid species have seed that can germinate without mycorrhiza, namely the species within the genus Disa with hydrochorous seeds.

As the chance for a seed to meet a suitable fungus is very small, only a minute fraction of all the seeds released grow into adult plants. In cultivation, germination typically takes weeks.

techniques have been devised for germinating orchid seeds on an artificial nutrient medium, eliminating the requirement of the for germination and greatly aiding the propagation of ornamental orchids. The usual medium for the sowing of orchids in artificial conditions is gel combined with a energy source. The carbohydrate source can be combinations of discrete sugars or can be derived from other sources such as , , , or even puree or . After the preparation of the agar medium, it is poured into or jars which are then autoclaved (or cooked in a pressure cooker) to sterilize the medium. After cooking, the medium begins to gel as it cools.


Taxonomy
The taxonomy of this family is in constant flux, as new studies continue to clarify the relationships between species and groups of species, allowing more at several to be recognized. The Orchidaceae is currently placed in the order by the APG III system of 2009.

Five are recognised. The below was made according to the of 1998. It represents the view that most botanists had held up to that time. It was supported by , but never received strong support in molecular phylogenetic studies.

In 2015, a study showed strong statistical support for the following of the orchid tree, using 9 of and from 7 , a topology that was confirmed by a study in the same year.


Evolution
A study in the scientific journal Nature has hypothesised that the origin of the orchids goes back much longer than originally expected. An extinct species of stingless bee, Proplebeia dominicana, was found trapped in from about 15-20 million years ago. The bee was carrying of a previously unknown orchid taxon, Meliorchis caribea, on its wings. This find is the first evidence of fossilised orchids to date and shows insects were active of orchids then. This extinct orchid, M. caribea, has been placed within the extant tribe , subtribe (subfamily ). An even older orchid species, Succinanthera baltica, was described from the by Poinar & Rasmussen (2017).

Genetic sequencing indicates orchids may have arisen earlier, 76 to 84 million years ago during the . "An overview of the Phalaenopsis orchid genome by BAC sequence analysis" (pdf format) . According to Mark W. Chase et al. (2001), the overall biogeography and phylogenetic patterns of Orchidaceae show they are even older and may go back roughly 100 million years.

(2024). 9780198507109, Oxford University Press.

Using the method, it was possible to determine the age of the major branches of the orchid family. This also confirmed that the subfamily is a branch at the basal dichotomy of the orchids, and must have evolved very early in the evolution of the family. Since this subfamily occurs worldwide in tropical and subtropical regions, from tropical America to tropical Asia, New Guinea and West Africa, and the continents began to split about 100 million years ago, significant biotic exchange must have occurred after this split (since the age of Vanilla is estimated at 60 to 70 million years). Recent biogeographic studies conducted on densely sampled phylogenies indicated that the most recent common ancestor of all extant orchids probably originated somewhere 83 million years ago in the supercontinent . Despite their long evolutionary history on Earth, the extant orchid diversity is also inferred to have originated during the last 5 million years, with the American and Asian tropics as the geopgraphic areas exhibiting the highest speciation rates (i.e., number of speciation events per million years) on Earth.

Genome duplication occurred prior to the divergence of this taxon.


Genera
There are around 800 genera of orchids. The following are amongst the most notable genera of the orchid family:


Etymology
The type genus (i.e. the genus after which the family is named) is . The genus name comes from the ὄρχις]] ( órkhis), literally meaning "", because of the shape of the twin tubers in some species of Orchis.
(1980). 9788424913328, Ed. Gredos. .
(1995). 9780198661894, Oxford University Press.
The term "orchid" was introduced in 1845 by in School Botany, Online Etymology Dictionary, "orchid". as a shortened form of Orchidaceae.
(1973). 9780713904420, Allen Lane.

In , the name bollockwort was used for some orchids, based on "" meaning testicle and "" meaning plant.


Hybrids
Orchid species hybridize readily in cultivation, leading to a large number of hybrids with complex naming. Hybridization is possible across genera, and therefore many cultivated orchids are placed into . For instance, the nothogenus × Brassocattleya is used for all hybrids of species from the genera and . Nothogenera based on at least three genera may have names based on a person's name with the suffix , for instance × Colmanara = × × . (The suffix is obligatory starting at four genera.International Code of Nomenclature for Cultivated Plants 9th edition (2016), Article H.6 and H.7.)

Cultivated hybrids in the orchid family are also special in that they are named by using grex nomenclature, rather than nothospecies. For instance, hybrids between Brassavola nodosa and Brassavola acaulis are placed in the grex Brassavola Guiseppi. Brassavola Guiseppi Casa Luna 1968, BlueNanta. The name of the grex ("Guiseppi" in this example) is written in a non-italic font without quotes.International Code of Nomenclature for Cultivated Plants 9th edition, 2016.


Abbreviations
As a unique feature of the orchid family, a system of abbreviations exists that applies to names of genera and nothogenera. The system is maintained by the Royal Horticultural Society. These abbreviations consist of at least one character, but may be longer. As opposed to the usual one-letter abbreviations used for names of genera, orchid abbreviations uniquely determine the (notho)genus. They are widely used in cultivation. Examples are Phal for , V for and Cleis for .


Distribution
Orchidaceae are cosmopolitan, occurring in almost every habitat apart from . The world's richest diversity of orchid genera and species is found in the , but they are also found above the , in southern , and two species of on at 54° south.

The following list gives a rough overview of their distribution:

  • Oceania: 50 to 70 genera
  • North America: 20 to 26 genera
  • tropical America: 212 to 250 genera
  • tropical Asia: 260 to 300 genera
  • tropical Africa: 230 to 270 genera
  • Europe and temperate Asia: 40 to 60 genera


Ecology
A majority of orchids are , which grow anchored to or in the and subtropics. Species such as sororium are , growing on rocks or very rocky soil. Other orchids (including the majority of Orchidaceae) are terrestrial and can be found in habitat areas such as grasslands or forest.

Some orchids, such as and , lack , so are unable to photosynthesise. Instead, these species obtain energy and nutrients by soil fungi through the formation of orchid mycorrhizae. The fungi involved include those that form with trees and other woody plants, parasites such as , and . These orchids are known as , but were formerly (incorrectly) described as saprophytes as it was believed they gained their nutrition by breaking down organic matter. While only a few species are achlorophyllous , all orchids are myco-heterotrophic during germination and seedling growth, and even photosynthetic adult plants may continue to obtain carbon from their fungi. The symbiosis is typically maintained throughout the lifetime of the orchid because they depend on the fungus for nutrients, sugars and minerals.


Uses

Perfumery
The of orchids is frequently analysed by (using headspace technology and gas-liquid chromatography/mass spectrometry) to identify potential fragrance chemicals.


Horticulture
The other important use of orchids is their cultivation for the enjoyment of the flowers. Most cultivated orchids are or , but quite a few that grow in colder climates can be found on the market. Temperate species available at nurseries include (bee orchid), Gymnadenia conopsea (fragrant orchid), Anacamptis pyramidalis (pyramidal orchid) and Dactylorhiza fuchsii (common spotted orchid).

Orchids of all types have also often been sought by collectors of both species and hybrids. Many hundreds of societies and clubs worldwide have been established. These can be small, local clubs, or larger, national organisations such as the American Orchid Society. Both serve to encourage cultivation and collection of orchids, but some go further by concentrating on conservation or research.

The term "botanical orchid" loosely denotes those small-flowered, tropical orchids belonging to several genera that do not fit into the "florist" orchid category. A few of these genera contain enormous numbers of species. Some, such as and , contain approximately 1700 and 2000 species, respectively, and are often extremely vegetatively diverse. The primary use of the term is among orchid hobbyists wishing to describe unusual species they grow, though it is also used to distinguish naturally occurring orchid species from horticulturally created hybrids.

New orchids are registered with the International Orchid Register, maintained by the Royal Horticultural Society.


Food
The dried seed pods of one orchid genus, Vanilla (especially Vanilla planifolia), are commercially important as a flavouring in , for manufacture and .

The underground tubers of terrestrial orchids mainly are ground to a powder and used for cooking, such as in the hot beverage or in the mastic ice cream . The name salep has been claimed to come from the expression , "fox testicles", but it appears more likely the name comes directly from the Arabic name . The similarity in appearance to testes naturally accounts for salep being considered an aphrodisiac.

The dried leaves of Jumellea fragrans are used to flavour rum on .

Some saprophytic orchid species of the group produce potato-like tubers and were consumed as food by native peoples in and can be successfully cultivated, notably Gastrodia sesamoides. Wild stands of these plants can still be found in the same areas as early Aboriginal settlements, such as Ku-ring-gai Chase National Park in . Aboriginal peoples located the plants in habitat by observing where had scratched in search of the tubers after detecting the plants underground by scent.


Cultural symbolism
Orchids have many associations with symbolic values. For example, the orchid is the City Flower of , China. is the national Venezuelan flower, while is the national flower of . Vanda Miss Joaquim is the national flower of , Guarianthe skinneri is the national flower of and Rhyncholaelia digbyana is the national flower of . Prosthechea cochleata is the national flower of , where it is known as the black orchid. has a white variety (alba) that is the national flower of , commonly known as Monja Blanca (White Nun). 's national flower is the Holy Ghost orchid ( ), or 'the flor del Espiritu Santo'. Rhynchostylis retusa is the state flower of the Indian state of where it is known as Kopou Phul.

Orchids native to the Mediterranean are depicted on the in Rome, until now the only known instance of orchids in ancient art, and the earliest in European art. A French writer and agronomist, , invented a classical myth in his book Le Jardinier Fleuriste et Historiographe published in 1704, attributing it to the ancient Greeks and Romans, in which Orchis the son of a nymph and a satyr rapes a priestess of during one of his festivals the Bacchanalia and is then killed and transformed into an orchid flower as punishment by the gods, paralleling the various myths of youths dying and becoming flowers, like and Narcisuss; this myth however does not appear any earlier than Liger, and is not part of traditional Greek and Roman mythologies.

(2016). 9780226376325, University of Chicago Press. .

A and B Larsen orchids - Cattleya Mrs Mahler Mem Fred Tompkins 659-9.jpg| Cattleya Mrs. Mahler 'Mem. Fred Tompkins' File:A and B Larsen orchids - Cattleya Queen Sirikhit Diamond Crown DSCN4414.JPG| Cattleya Queen 'Diamond Crown' A and B Larsen orchids - Cattleya Hawaiian Wedding Song Virgin 674-23.jpg| Cattleya Hawaiian Wedding Song 'Virgin' Blc Chia-lin.jpg| Rhyncholaeliocattleya Chia Lin

A and B Larsen orchids - Cattleya Hawaian Variable Prasan 336-2.jpg| Cattleya Hawaiian Variable 'Prasan' File:A and B Larsen orchids - Cattleya Barbara Belle DSCN8696.JPG| Cattlianthe Barbara Belle File:Cattleya Beaumesnil Parme 1001 Orchids.jpg| Cattleya Beaumesnil 'Parme' File:A and B Larsen orchids - Cattleya Chocolate Drop x Pao de Acucar 507-21.jpg| Cattlianthe Chocolate Drop x Cattleya Pão de Açúcar File:Cattleya Empress Frederick C mossiae.jpg| 'Empress Frederick' File:Cattleya Hermine.jpg|'Hermine' File:A and B Larsen orchids - Cattleya Little AngelDSCN3349.JPG| Cattleya Little Angel File:A and B Larsen orchids - Cattleya Marjorie Hausermann York 812-4.jpg| Cattleya Marjorie Hausermann 'York' File:A and B Larsen orchids - Cattleya Miva Breeze Alize 930-23.jpg|'Miva Breeze Alize' File:Blc Nobiles carnival.jpg| Rhyncholaeliocattleya 'Nobile's carnival' File:Cattleya Pernell George Barnett "Yankee Clipper" (3072486817).jpg| Cattleya Pernel George Barnett 'Yankee Clipper' File:Cattleya Portia.jpg| Cattlianthe Portia


Conservation
Almost all orchids are included in Appendix II of the (CITES), meaning that international trade (including in their parts/derivatives) is regulated by the CITES permit system. A smaller number of orchids such as Paphiopedilum sp. are listed in CITES Appendix I meaning that commercial international trade in wild-sourced specimens is prohibited and all other trade is strictly controlled.


Assisted migration as conservation tool
In 2006 the was constructed at the , near the Yachang Orchid Nature Reserve. In response to threats of of wild orchids at lower altitudes (350-400 m above sea level), 1000 endangered orchid plants of 16 genera and 29 species were translocated to higher elevation (approximately 1000 m above sea level). After relocation the 5 year survival of low and wide elevation species did not significantly differ and the mortality due to was at only 10%. From this it was concluded that assisted migration might be a viable conservation tool for orchid species endangered by .


See also
  • Adaptation (film), based on The Orchid Thief
  • Orchid Conservation Coalition
  • Orchid Pavilion Gathering
  • , the Victorian era of flower madness in which collecting and discovering orchids reached extraordinary levels
  • Orchids of the Philippines
  • Orchids of Western Australia
  • Black rot on orchids
  • List of taxa named after human genitals


Notes

Bibliography

Documentaries
  • 2017: Hidden Beauty – The Orchids of the Saale Valley, directed by


External links

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