Orchids are plants that belong to thefamilyOrchidaceae (/ˌɔːrkɪˈdeɪsi.iː,-si.aɪ/),[2] a diverse and widespread group offlowering plants with blooms that are often colourful and fragrant. Orchids arecosmopolitan plants, living in diverse habitats on every continent except Antarctica. The world'srichest diversity of orchid genera and species is in thetropics. Many species areepiphytes, living on trees. The flowers and their pollination mechanisms are highly specialized, attracting insect pollinators by colour, pattern, scent, pheromones, and sometimes bymimicking female insects. Orchids have very small seeds, relying on fungal partners for germination. Some orchids have no leaves, either photosynthesizing with their roots or relying entirely on fungal partners for food.
Orchidaceae is one of the two largest families of flowering plants. It contains about 28,000 currently accepted species in around 700 genera.[3][4] That represents some 6–11% of all species ofseed plants.[5]Horticulturists run many orchid societies around the world; they have produced manyhybrids andcultivars.
Thetypegenus (i.e. the genus after which the family is named) isOrchis. The genus name comes from theAncient Greekὄρχις (órkhis), literally meaning "testicle", because of the shape of the twin tubers in some species ofOrchis.[6][7][8] The term "orchid" was introduced in 1845 byJohn Lindley inSchool Botany,[9] as a shortened form ofOrchidaceae.[10] InMiddle English, the namebollockwort was used for some orchids, based on "bollock" meaning testicle and "wort" meaning plant.[11]
All orchids areperennialherbs that lack any permanentwoody structure. They can grow according to two patterns:[13][15]
Monopodial: The stem grows from a single bud, leaves are added from the apex each year, and the stem grows longer accordingly, as inVanda.[15]
Sympodial: growth is at a front, with older growth behind, at a "back".[16] Sympodial orchids may have swollenpseudobulbs.[15]
Terrestrial (ground-living) orchids may haverhizomes ortubers.[13]Epiphytic orchids, those that grow upon a support, haveaerial roots. The older parts of the roots are covered with avelamen, a layer of dead cells.[13]
Like mostmonocots, orchids usually have simple (untoothed)leaves withparallel veins.[17] Some orchids such asVanda aredistichous, with their leaves arranged in two ranks on opposite sides of the stem.[18] This is the arrangement at the base of all orchid shoots, though in many species the leaves higher up the shoot switch to a spiralphyllotaxis.[19] Orchids are perennial; most species add new leaves at the apex while the oldest leaves gradually die off,[20] but some such asCatasetumshed their leaves annually in the dry season, developing new leaves and new pseudobulbs each year.[21]
Some epiphytic orchids, such asTaeniophyllum aphyllum, are leafless, depending on their green roots forphotosynthesis.[22] Other epiphytes likePhalaenopsis have leaves, but rely on photosynthesis in their green roots to prevent hypoxia (lack of oxygen) of the roots.[22] Orchids of the genusCorallorhiza (coralroot orchids) have no leaves; instead they have symbiotic or parasitic associations with fungal mycelium, through which they absorb sugars.[23]
Leaves ofVanda aredistichous, arranged in two opposite ranks.
Orchid flowers are very varied in form. They have threesepals, three petals and a three-chamberedovary. The three sepals and two of the petals are often similar to each other but one petal is usually highly modified, forming a "lip" orlabellum. In most orchid genera, as the flower develops, it undergoes a twisting through 180°, calledresupination, so that the labellum lies below thecolumn. The labellum functions to attract insects, and in resupinate flowers, also acts as a landing stage, or sometimes a trap.[24][25][12][26]
The reproductive parts of an orchid flower are unique in that thestamens andstyle are joined to form a single structure, thecolumn.[12][26][29]
Most orchids deliver pollen in a single mass, apollinium (plural: pollinia), able to fertilise thousands of ovules.[30]The pollinia are attached to a sticky disc near the top of the column. Just below the pollinia is a second, larger sticky plate, thestigma.[24][25][12][26]
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 is so placed that it sticks to the stigma of the second flower, pollinating it.[27] In horticulture,artificial orchid pollination 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.[31]
Pollinators are often visually attracted by the shape and colours of the labellum. However, someBulbophyllum species attract male fruit flies (Bactrocera andZeugodacus spp.) solely via a floral chemical which simultaneously acts as a floral reward (e.g.methyl eugenol, raspberryketone, orzingerone) to perform pollination.[32][33][34]
The slipper orchidPaphiopedilum parishii reproduces byself-fertilization. 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.[35]
In some extremely specialized orchids, such as the Eurasian genusOphrys, the labellum is adapted to have a colour, shape, and odour which attracts male insects viamimicry of a receptive female. Pollination happens as a male insect attempts to mate with the flowers.[36][37][38][39]
Many neotropical orchids are pollinated by maleorchid bees, which visit the flowers to gather volatile chemicals they require to synthesizepheromonal attractants. Males of species such asEuglossa imperialis orEulaema meriana leave their territories periodically to forage for aromatic compounds, such ascineole, to synthesizepheromone for attracting females.[40][41]
Catasetum saccatum, discussed by Darwin, launches its viscid pollinia with explosive force when an insect touches aseta, knocking the pollinator off the flower.[42]
Orchid bees such asEuglossa viridissima collect aromatic compounds on their hind legs as they pollinate neotropical orchids.[40][41]
When a bee touches aseta (a trigger hair) on the flower ofCatasetum saccatum, the sticky pollinia are shot explosively at the insect.[42]
Some species, such as in the generaPhalaenopsis,Dendrobium, andVanda, produce offshoots or plantlets formed from one of thenodes along thestem, through the accumulation of growth hormones at that point. These shoots are known to horticulturalists askeiki.[43]
Epipogium aphyllum exhibits a dual reproductive strategy, engaging in both sexual and asexual seed production. The likelihood ofapomixis 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.[44]
Akeiki plantlet at the apex of aPhalaenopsis orchid, ready to be cut and planted
The ovary develops into acapsule that isdehiscent by three or six longitudinal slits in its sides.[13]
Theseeds of orchids are 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 lackendosperm in their seed and must enter symbiotic relationships with variousmycorrhizalbasidiomyceteousfungi that provide them the necessary nutrients to germinate, so almost all orchid species aremycoheterotrophic during germination and reliant upon fungi to complete their lifecycles. Only a handful of orchid species have seed that can germinate withoutmycorrhiza, namely the species within the genusDisa withhydrochorous seeds.[45]
Few orchid fossils are recorded. An extinct species of stingless bee,Proplebeia dominicana, was found trapped inMioceneamber from about 15–20 million years ago. The bee was carryingpollen of a previously unknown orchid taxon,Meliorchis caribea, on its wings. This 2007 find provided the first fossil evidence of orchids.[46] It shows insects were activepollinators of orchids in the Miocene.M. caribea has been placed within the extant tribeCranichideae, subtribeGoodyerinae (subfamilyOrchidoideae). An even older orchid species,Succinanthera baltica, was described in 2017 fromBaltic amber ofEocene age, some 40–55 million years ago.[47]
Genetic sequencing indicates orchids may have arisen earlier, 76 to 84 million years ago during theLate Cretaceous.[48] According toMark W. Chaseet al. (2001), the overall biogeography and phylogenetic patterns of Orchidaceae show they are even older and may go back roughly 100 million years.[49]
Themolecular clock method has provided ages for the major branches of the orchid family. The subfamilyVanilloideae is a branch at the base of themonandrous orchids, and must have evolved very early in the evolution of the family, some 60 to 70 million years ago. 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. Biogeographic studies indicate that themost recent common ancestor of all extant orchids probably originated 83 million years ago somewhere in the supercontinentLaurasia. 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 geographic areas exhibiting the highest speciation rates (i.e., number of speciation events per million years) on Earth.[50]
Genome duplication occurred prior to the divergence of this taxon.[51]
Thecladogram below was made according to theAPG system of 1998. It represents the view that most botanists had held up to that time. It was supported bymorphological studies.[52]
The orchids are among the largest and most diverse taxonomic groups of vascular plants, withat least 700 genera[3][55] and 28,000 species; they are rivalled only by theAsteraceae (Compositae) which has some 1,600 genera and around 24,700 species, and new species are continually being discovered and described.[3] In 1753,Carl Linnaeus recognized eight genera of orchids in hisSpecies Plantarum.[56]Antoine Laurent de Jussieu recognized the Orchidaceae as a separatefamily in hisGenera Plantarum in 1789.[57]Olof Swartz recognized 25 genera in 1800.[58][59] In 1830–1840,John Lindley recognized foursubfamilies.[60]The family was placed in theorderAsparagales by theAPG III system of taxonomy of 2009, mainly usingmolecular phylogenetics, where fivesubfamilies are recognised.[1][a] The diversity of orchids led taxonomists to create hundreds of genera. Some taxonomists felt that the number had become excessive, and published classifications with fewer genera. Dressler had some 850 genera in 2013;[62]Genera Orchidacearum reduced this to 765 in 2014;[63] and Chase continued the process of merging genera, with 736 in 2015.[64]
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 intonothogenera. For instance, the nothogenus×Brassocattleya is used for all hybrids of species from the generaBrassavola andCattleya. Nothogenera based on at least three genera may have names based on a person's name with the suffix-ara, for instance×Colmanara=Miltonia ×Odontoglossum ×Oncidium. The suffix is obligatory starting at four genera.[65]
Cultivated hybrids in the orchid family are also special in that they are named by usinggrex nomenclature, rather than nothospecies. For instance, hybrids betweenBrassavola nodosa andBrassavola acaulis are placed in the grexBrassavola Guiseppi.[66] The name of the grex ("Guiseppi" in this example) is written in a non-italic font without quotes.[65]
Some orchids, such asNeottia andCorallorhiza, lackchlorophyll, so are unable to photosynthesise. Instead, these species obtain energy and nutrients byparasitising soil fungi through the formation oforchid mycorrhizae. The fungi involved include those that formectomycorrhizas with trees and other woody plants, parasites such asArmillaria, andsaprotrophs.[69] These orchids are known asmyco-heterotrophs, 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 achlorophyllousholoparasites, all orchids are myco-heterotrophic during germination and seedling growth, and even photosynthetic adult plants may continue to obtain carbon from theirmycorrhizal fungi.[70][71] The symbiosis is typically maintained throughout the lifetime of the orchid because they depend on the fungus for nutrients, sugars and minerals.[72]
Orchidsemploy multiple forms of deception to attract pollinators. Some produce the aroma of nectar without providing the actual food reward. Others attractnematoceran gnats which feed on decaying fungi with the aroma of mushrooms. Others again produce the aroma of female insects, attracting male insects toattempt to copulate. In each case the orchid is pollinated by an insect that is deceived and that does not receive the expected reward.[73]
Many orchid species and hybrids are cultivated for their flowers. Most of these are tropical or subtropical, needing to be grown indoors in temperate zones, but some such as species ofCypripedium andDactylorhiza can be grown outdoors in temperate climates.[74] Several thousand newcultivated orchid hybrids are registered each year.[75]
A large number of societies and clubs for orchid growers are run in countries in all continents except Antarctica.[76] National societies include the Orchid Society of Great Britain[77] and theAmerican Orchid Society.[78] New orchids are registered with the International Orchid Register, maintained by theRoyal Horticultural Society.[79] An annual festival of orchids is held in February every year at theRoyal Botanic Gardens, Kew.[80]
The tubers of terrestrial orchids (mainly early purple orchid,Orchis mascula) are ground to a powder and used for cooking, such as in the hot beveragesalep andice cream,[85] leading to local extinctions in parts of Greece, Turkey, and Iran.[86] Some saprophytic orchid species of the groupGastrodia produce potato-like tubers and were eaten by native peoples in Australia and can be cultivated, notablyGastrodia sesamoides. Wild stands of these plants still grow near early Aboriginal settlements, such asKu-ring-gai Chase National Park.Aboriginal peoples found the plants by observing wherebandicoots had scratched in search of the tubers after detecting the plants by scent.[87]
Orchids have symbolic values in some cultures; several countries have chosen orchids as theirnational flowers.[89][90][91] Because of the etymology of the word "orchid", and the use oforchiectomy, a surgery onintersex infants, the orchid has become a symbol of being intersex and of opposition to non-consensual genital surgery.[92]
Orchids native to the Mediterranean are depicted on theAra Pacis in Rome, until now the only known instance of orchids in ancient art, and the earliest in European art.[93] A French writer and agronomist,Louis Liger, invented a classical myth in his bookLe Jardinier Fleuriste et Historiographe published in 1704, attributing it to the ancient Greeks and Romans, in whichOrchis the son of a nymph and a satyr rapes a priestess ofBacchus 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, likeAdonis andNarcissus; this myth however does not appear any earlier than Liger, and is not part of traditional Greek and Roman mythologies.[94]
Almost all orchids are included in Appendix II of theConvention on International Trade in Endangered Species (CITES),[95] meaning that international trade is regulated by the CITES permit system.[96] A smaller number of orchids, such asPaphiopedilum species, are listed in CITES Appendix I, meaning that commercial international trade in wild-sourced specimens is prohibited and other trade is strictly controlled.[96]
Assisted migration may be a viable conservation tool for orchids endangered byclimate change. In 2006 theLongtan Dam was built near theYachang Orchid Nature Reserve. In response to the threat ofinundation at lower altitudes (350–400 m), 1000 endangered orchid plants of 16 genera and 29 species were translocated to higher elevation (around 1000 m), where they survived well.[97]
^A unique feature of the orchid family is a system of abbreviations for names of genera and nothogenera. The system is maintained by theRoyal Horticultural Society.[61]
^"Orchid Tree: a phylogeny of epiphytes (mostly) on the tree of life"(PDF).University of Florida Herbarium. August 2021. p. 111. Retrieved24 August 2025.Phyllotaxy in orchids is described as either spiral or distichous, with the latter supposed to be the more advanced state (Dressler & Dodosn, 1960; Dressler, 1993). We found that in all species examined, the condition at the base of a stem, represented by the first bracts surrounding a bud, is distichous.
^Jenny King (10 June 2011)."The coralroot orchid".Orchids in Northern Washington State. Silvercrown Mountain Outdoor School. Archived from the original on 21 October 2011. Retrieved10 June 2011.
^abHoffman, Noel; Brown, Andrew (August 2011).Orchids of South-West Australia (3rd ed.). Gooseberry Hill: Noel Hoffman. p. 13.ISBN978-0-646-56232-2.
^abBrown, Andrew; Dixon, Kingsley; French, Christopher; Brockman, Gary (2013).Field guide to the orchids of Western Australia: the definitive guide to the native orchids of Western Australia. Floreat, Western Australia: Simon Nevill Publications. pp. 16–17.ISBN978-0-9803481-4-9.
^abcZimmermann, Pedro."Anatomy of an Orchid". Brasilian Orchid Organisation. Retrieved15 April 2022.
^Tan, Keng-Hong; Nishida, Ritsuo; Toong, Yock-Chai (June 2002). "Floral Synomone of a Wild Orchid, Bulbophyllum cheiri, Lures Bactrocera Fruit Flies for Pollination".Journal of Chemical Ecology.28 (6):1161–1172.Bibcode:2002JCEco..28.1161T.doi:10.1023/A:1016277500007.PMID12184394.
^Stokl, J.; Schluter, P. M.; Stuessy, T. F.; Paulus, H. F.; Fraberger, R.; Erdmann, D.; Schulz, C.; et al. (2009). "Speciation in sexually deceptive orchids: pollinator-driven selection maintains discrete odour phenotypes in hybridizing species".Biological Journal of the Linnean Society.98 (2):439–451.doi:10.1111/j.1095-8312.2009.01279.x.
^Ramírez, Santiago R.; Gravendeel, Barbara; Singer, Rodrigo B.; Marshall, Charles R.; Pierce, Naomi E. (30 August 2007). "Dating the origin of the Orchidaceae from a fossil orchid with its pollinator".Nature.448 (7157):1042–1045.Bibcode:2007Natur.448.1042R.doi:10.1038/nature06039.PMID17728756.
^Chase, Mark W. (2001). "The origin and biogeography of Orchidaceae". In A. M. Pridgeon; P. J. Cribb; M. W. Chase; F. Rasmussen (eds.).Orchidoideae (Part 1). Genera Orchidacearum. Vol. 2.Oxford University Press. pp. 1–5.ISBN978-0-19-850710-9.
^de Jussieu, Antoine Laurent. 1789. "ORCHIDEAE" pages 64-66. In:Genera plantarum: secundum ordines naturales disposita.
^Swartz, Olof. 1800. "Afhandling om Orchidernes Slägter och deras Systematiska indelning" [Treatise on the Types of Orchids and Their Systematic Arrangement].Kongliga vetenskaps academiens nya handlingar, vol. 21, pages 115-139.
^Mark W. Chase, Kenneth M. Cameron, John V. Freudenstein, Alec M. Pridgeon, Gerardo A. Salazar, Cássio van den Berg, and André Schuiteman. 2015. "An updated classification of Orchidaceae".Botanical Journal of the Linnean Society177 (2): 151-174.
^Leake, Jonathan R. (August 2005). "Plants parasitic on fungi: unearthing the fungi in myco-heterotrophs and debunking the 'saprophytic' plant myth".Mycologist.19 (3):113–122.doi:10.1017/S0269-915X(05)00304-6.
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![Orchid bees such as Euglossa viridissima collect aromatic compounds on their hind legs as they pollinate neotropical orchids.[40][41]](/mt/?noimg=&dark=on&url=http%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aOrchid_Bee_Sleeping_on_Leaf.jpg)
![When a bee touches a seta (a trigger hair) on the flower of Catasetum saccatum, the sticky pollinia are shot explosively at the insect.[42]](/mt/?noimg=&dark=on&url=http%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aCatasetum-saccatum.jpg)
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![Orchid cornucopia in the annual festival of orchids at the Royal Botanic Gardens, Kew[80]](/mt/?noimg=&dark=on&url=http%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aCornucopia_of_Orchids_at_Kew.jpg)
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