Orchid

Orchidaceae is one of the largest families of flowering plants, with more than 28,000 accepted species in 763 genera. Orchids occur on almost every continent and in nearly every habitat.

The orchid family is the largest family listed under CITES, with a figure of around 30,000 species given in that context. Counts of accepted species differ between authorities: more than 28,000 accepted species are placed in 763 genera, while Kew gives a figure of about 27,800 species. The family is divided into five subfamilies, and the slipper orchids, Cypripedioideae, occupy a position within that arrangement.

Cypripedioideae comprises about 182 recognised species. Within the group, Cypripedium is the most widespread slipper genus, with 52 species whose range extends from North and Central America to Europe and Asia.

China's orchid flora is the richest in Asia after Indonesia and Malaysia, with more than 1,700 species recorded there. The island of Madagascar holds a comparable concentration of diversity in a far smaller area: roughly one in ten of its 10,000 to 12,000 vascular plant taxa is an orchid, and most of these are endemic. Within Madagascar the Itremo Massif functions as a micro-hotspot, sheltering more than 50 orchid taxa.

The American tropics support about 7,000 orchid species, a fifth of the world total, a radiation that arose only 15 to 20 million years ago. The Andes concentrate about 15% of the world's plant species on only 1% of the earth's surface. Andean orchids are therefore very young compared with the first appearance of orchids about 110 million years ago.

For more than a century, scientists assumed that epiphytes were mostly widespread because of their remarkable dispersal abilities.

Researchers assembled a 5.2 Gb chromosome-scale genome of Ophrys sphegodes, the early spider-orchid. A burst of transposon activity in the Ophrys genome preceded the group's adaptive radiation. The labellum pattern is thought to be involved in aversive learning that increases outcrossing, not in attracting males.

Epiphytes perch on bark or nestle among branches, drawing the moisture they need from rain and fog. They may resemble parasites, yet they neither harm nor benefit the trees that carry them. The moth orchid is a familiar epiphytic houseplant.

The velamen radicum, a unique dead structure on the root surfaces of most epiphytic orchids, is made of dead air-filled cells and is thought to act like blotting paper. Pseudobulbs store water through dry spells. The velamen and mycorrhizal fungi can compensate for the lack of root hairs in absorbing nutrients from the air.

Orchid seeds are among the smallest produced by any flowering plant, ranging from 0.25 mm to 1.2 mm in length. Each is little more than a seed coat enclosing a rudimentary embryo composed of 80 to 300 undifferentiated cells. The embryo is not organized into the distinct tissues — root, shoot, and leaf primordia — that characterize the seeds of most other plants, and the seed carries no stored food reserve to sustain the young plant after it begins to grow.

Because the embryo cannot draw on its own reserves, germination in nature depends entirely on the seed forming a mycorrhizal association with an appropriate fungus, which supplies the carbon and nutrients the seedling requires. Lewis Knudson's 1922 paper described the nutrient medium that made large-scale orchid breeding possible, freeing growers from reliance on the fungus. Nearly all orchids grown from seed at Kew are germinated in vitro, a technique used there since the 1980s. For critically endangered species, however, seed baiting to find fungal partners can be too wasteful, since few packets yield seedlings.

The genus Ophrys comprises about 260 species, nearly all sexually deceptive and usually attracting males of a single species. The pink perianth of Ophrys heldreichii increases detectability by its pollinator, males of the long-horned bee Eucera berlandi. The orchid mimics the female insect's hairs, wings and pheromones to lure males into pseudocopulation, a species-specific strategy called sexual deception.

About 250 species of orchid bees pollinate thousands of tropical American plants, roughly a third of the local flora.

In the bucket orchid Coryanthes, a bee slips on the waxy, smooth mesochil and falls into the fluid-filled, bucket-like epichil; the only way out is a tunnel, where the bee first contacts the stigma and then the anther, which glues pollinaria onto its thorax. A female Euglossa dilemma bee found dead in a Coryanthes flower still carried the orchid's pollinarium.

Angraecum sesquipedale is known as Darwin's orchid for the theory that a not-yet-discovered moth pollinated it. The recently described Solenangis impraedicta carries a nectar spur reaching 33 cm, the third longest spur ever recorded in flowering plants and the longest relative to flower size. Its name impraedicta means unpredicted in Latin, a nod to the 130 years it took to confirm Darwin's prediction.

For 20 years after vanilla reached La Réunion the plants stayed infertile because no natural pollinator was present. Albius used a stick to lift the wall separating the flower's male and female organs and rub them gently together.

Curing runs through blanching, sweating, drying and conditioning. Blanching destroys cell and tissue structure so flavour precursors dissolve out. The enzyme beta-glucosidase was not detected in blanched or sweating beans but appeared after drying. Vanillin content rose from 0.03% in green beans to 2.69% in drying beans, with a peak of 2.97% in the fully cured beans of the study. Vanillin is formed by hydrolysis of glucovanillin or oxidation of vanillyl alcohol. After drying the beans are conditioned in closed wooden boxes at room temperature for six months.

Nearly 60% of orchid species may be at risk of extinction, far higher than for flowering plants overall.

The entire orchid family is listed under CITES so that international trade does not harm wild populations.

Conservation practice combines ex situ storage, propagation, reintroduction and conservation genetics. Around half a billion orchid plants are produced each year in commercial horticulture, a scale that could help prevent extinction.

Only about 2% of orchid species had been assessed for the IUCN Red List, compared with all conifers and all carnivorous plants. A Red List assessment of the slipper genus Cypripedium found 79% of its species threatened, with 46% of them endangered.

The slipper genera Paphiopedilum and Phragmipedium are listed in CITES Appendix I, so trade in them is prohibited except for non-commercial purposes or for artificially propagated plants.

A CITES-commissioned review identified 374 documented edible orchid species. Protection of areas such as national parks has not prevented the harvesting of Chikanda orchids inside them, and CITES parties are urged to create Non-detriment Findings for trade in edible orchid products.

The Cayman ghost orchid Dendrophylax fawcettii is leafless, with white flowers that appear to float in mid-air.

Singapore's orchid collection gained a dedicated nursery and orchid house in 1899, growing from a modest 1870s beginning under Henry Ridley.

The Missouri Botanical Garden's orchid story began when the first specimens were given to Henry Shaw in the early 1870s.

• 1834
  Darwin collects Chloraea magellanica
  Charles Darwin collects Chloraea magellanica on Chile's Elisabeth Island.
• 1870s
  Early collections in St. Louis and Singapore
  The first orchid specimens are given to Henry Shaw, while Singapore's collection has a modest beginning under Henry Ridley.^{15Orchids (Notable Plant Collections) · Missouri Botanical Garden ↗14National Orchid Garden · National Parks Board, Singapore Botanic Gardens ↗}
• 1899
  Singapore orchid house
  Singapore's orchid collection gains a dedicated nursery and orchid house.^{14National Orchid Garden · National Parks Board, Singapore Botanic Gardens ↗}
• 1922
  Knudson's nutrient medium paper
  Lewis Knudson publishes his paper on the nutrient medium.
• 1954
  First World Orchid Congress
  St. Louis hosts the first World Orchid Congress.
• 1995
  National Orchid Garden opens
  The National Orchid Garden opens.^{14National Orchid Garden · National Parks Board, Singapore Botanic Gardens ↗}
• 1999
  Paphiopedilum vietnamense discovered
  Paphiopedilum vietnamense is discovered.
• 2021
  Orchidetum added; Réunion vanilla protected
  The Tropical Montane Orchidetum is added to the National Orchid Garden, and Vanille de l'île de La Réunion is designated a protected geographical indication.^{14National Orchid Garden · National Parks Board, Singapore Botanic Gardens ↗}