Orchidaceae, also called the Orchid family, is the largest family of the flowering plants (Angiospermae).   This family is comprised of about 1,000 genera and more than 15,000 species. They are botanically considered herbs, since they do not produce wood.
- For list of genera see List of Orchidaceae genera
The Royal Botanical Gardens of Kew list 880 genera and nearly 22,000 accepted species, but the exact number is unknown (perhaps as much as 25,000)  because classification varies greatly in different segments of the academic world. The number of orchid species equals about four times the number of mammal and bird species together. It also encompasses about 6 - 11 % of all seed plants  About 800 new orchid species are added each year. The largest genera are Bulbophyllum (2,000 species), Epidendrum (1,500 species), Dendrobium (1,400 species) and Pleurothallis (1,000 species). The family also includes the Vanilla (the genus of the vanilla plant), Orchis (type genus) and many commonly cultivated plants like some Phalaenopsis or Cattleya.
Moreover, since the introduction of tropical species in the 19th century, horticulturists have more than 100,000 hybrids and cultivars.
Orchidaceae are cosmopolitan, occurring in almost every habitat apart from deserts and glaciers. The great majority are to be found in the tropics, mostly Asia, South America and Central America. They are found above the Arctic Circle, in southern Patagonia and even on Macquarie Island, close to Antarctica.
The following list gives a rough overview of their distribution:
- tropical America: 300 to 350 genera
- tropical Asia: 250 to 300 genera
- tropical Africa: 125 to 150 genera
- Oceania: 50 to 70 genera
- Europe and temperate Asia: 40 to 60 genera
- North America: 20 to 30 genera
The greatest diversity of orchid species occurs in tropical areas, notably in mountainous areas, due to the effect of reproductive isolation of plant species caused by the mountains. Islands generally provide favorable conditions for speciation but unless they are large enough to have a variety of climates, they tend to have just a few endemic species. Such unusually large islands include Borneo, New Guinea, and Madagascar, all of which exhibit a wealth of different species, many unique to their respective island. Due to these factors, the main areas noted for having a large number of orchid species include the islands of Southeast Asia, the mountainous areas of Ecuador and Colombia and the Atlantic Jungle along the Brazilian coastal mountains, where more than fifteen hundred species have been cataloged. Other important areas with considerable orchid diversity are the mountains of Mesoamerica, the peaks south of Himalaya in India and China, and the southeast of Africa, particularly Madagascar.
The three countries with the largest number of reported orchid species are Ecuador, with over 3,500.  Colombia, with over 2,700,  and Brazil, with over 2,500. Other orchid-rich places include New Guinea, which as a whole has over 2,700 species, Borneo, Sumatra, Madagascar, Venezuela and Costa Rica
Orchids can be separated into five types of growing conditions.
- Aquatic - plants that grow in the water.
- Epiphyte - plants that grow on branches and mossy trees.
- Lithophyte - plants that grow in rock outcrops and in stone surfaces
- Saprophytes - grows in leaf litter and is usually dependent on mycorrhiza for nuitrience
- Terrestrial - plants that grow in sand, clay, or soil
Epiphytic orchids do not root in soil, and assimilate all their water and nutrients from air and rain. Some species store water in thickened, succulent stems, called pseudobulbs, others have highly porous roots covered by a spongy layer that can absorb humidity from the air. Some species go through long periods of rest when their metabolism is slowed, followed by rapid growth when resources are abundant. Many species lose their leaves to avoid dehydration during droughts, or while they are resting.
Saprophytes orchids, like Neottia and Corallorhiza, lack chlorophyll and are unable to photosynthesize. Instead, these species obtain energy and nutrients by parasitising soil fungi through the formation of orchid mycorrhizas. The fungi involved include those that form ectomycorrhizas with trees and other woody plants, parasites such as Armillaria, and saprotrophs. These orchids are known as myco-heterotrophs, but were formerly (incorrectly) described as saprophytes due to the belief that they gained their nutrition by breaking down organic matter. While only a few species are achlorophyllous holoparasites, all orchids are myco-heterotrophic during germination and seedling growth and even photosynthetic adult plants may continue to obtain carbon from their mycorrhizal fungi.
- For details see Orchid Morphology
The basic orchid flower structure is composed of three sepals and two petals with a lip or labellum. The flower is usually bilaterally symmetric and a column which holds the pollina in the center.
Plants can be divided into two growth habits monopodial and sympodial. Sympodial orchids have a lateral growth habit while monopodial orchids grow up from a single point.
Orchids obtain their name of Greek "orchis", meaning "testicle", for the appearance of the underground tubercles in some terrestrial species. Its name is derived from the genus Orchis. The word "orchis" used Theophrastus for the first time (371/372 - 287/286 B.C.), in his book "De Historia Plantarum" (On the Natural History of Plants). He was student of Aristotle and it is considered the father of botany and ecology.
- For more information see Taxonomy of the Orchids
This family is universally recognised, and the APG II system of 2003 places it in the order Asparagales.
The taxonomy of this family is in constant flux, as new studies continue to identify more classificatory elements.
Largest orchid flower: Coryanthes bruchmuelleri
Smallest orchid flower: Platystele jungermannioides
Longest orchid flower: Paphiopedilum sanderianum
Largest orchid species: Grammatophyllum speciosum
Smallest orchid species: Bulbophyllum minutissimum
Largest genus: Bulbophyllum
- ↑ Number of orchids
- ↑ Orchid Fact File, Royal Botanic gardens, Kew
- ↑ CLASSIFICATION OF ORCHIDACEAE IN THE AGE OF DNA DATA
- ↑ [www.blackwell-synergy.com/doi/pdf/10.1111/j.1523-1739.2006.00573.x Taxonomic exaggeration and its effects on orchid conservation]
- ↑ Pabst G, Dungs F (1975) Orchidaceae Brasilienses vol. 1, Brucke-Verlag Kurt Schmersow, Hildesheim. ISBN 3871050106
- ↑ 6.0 6.1 6.2 Govaerts R, Campacci MA(Brazil, 2005), Holland Baptista D (Brazil, 2005), Cribb P (K, 2003), George A (K, 2003), Kreuz K (2004, Europe), Wood J (K, 2003, Europe) World Checklist of Orchidaceae. The Board of Trustees of the Royal Botanic Gardens, Kew. Checklists by region and Botanical countries.Published on Internet access 1st March 2009.
- ↑ Govaerts R et al. World Checklist of Orchidaceae. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on Internet access 1st March 2009.
- ↑ Hoehne FC (1940) Flora Brasílica Fascículo 1, Volume 12.1; 1 a 12 - Orchidaceae, introdução.
- ↑ Leake JR. 2005. Plants parasitic on fungi: unearthing the fungi in myco-heterotrophs and debunking the ‘saprophytic’ plant myth. Mycologist 19: 113–122. (abstract)).
- Walter S. Judd, Christopher S. Campbell, Elizabeth A. Kellogg, Peter F. Stevens, Michael J. Donoghue: Plant Systematics: A Phylogenetic Approach, Sinauer Associates Inc. 2007
- Batygina, T. B., Bragina, E. A., and Vasilyeva, E. 2003. The reproductive system and germination in orchids. Acta Biol. Cracov. ser. Bot. 45: 21-34.
- Berg Pana, H. 2005. Handbuch der Orchideen-Namen. Dictionary of Orchid Names. Dizionario dei nomi delle orchidee. Ulmer, Stuttgart
- Kreutz, C. A. J. 2004. Kompendium der Europaischen Orchideen. Catalogue of European Orchids. Kreutz Publishers, Landgraaf, Netherlands
- Ramírez, S., et al. Nature 448 , 1042- 1045 (2007).
- D. Lee Taylor and Thomas D. Bruns : Ectomycorrhizal mutualism by two nonphotosynthetic orchids; Proc. Natl. Acad. Sci. USA; Vol. 94, pp. 4510-4515, April 1997 (on line).
- Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 7, May 2006 [and more or less continuously updated since]. 
- Strasburger, Noll, Schenck, Schimper: Lehrbuch der Botanik für Hochschulen. 4. Auflage, Gustav Fischer, Jena 1900, p. 459
- American Orchid Society - Orchid Web
- Auckland Orchid Club
- Austrian Orchid Society
- Cymbidium Orchids
- Kew checklist
- Native Orchid Conservation Inc
- Orchids of Europe
- Orchids of Kerala
- Orchid Photo Encyclopedia
- Orchid Picture Gallery
- OrchidWorks - a photo album and overview of a variety of orchids
- Orange County (California) Orchid Society
- Peloric "Two Lips" Phalaenopsis
- Peruvian Orchids - Mayumi Hashi, a botanical illustrator's report on a trip to Peru, which was partly funded by the Royal Horticultural Society (RHS).
- Report on pollination tactics by orchids
- Revealing the secret life of orchids ( Centre for plant biodiversity research - CSIRO and Botanic Gardens Australia )
- Royal Horticultural Society (RHS) International Orchid Register (with search capability)
- Swiss Orchid Foundation at the Herbarium Jany Renz
- Tasmanian terrestrial orchids (Hobart District Group of The Australian Plants Society)
- Waling-waling, an endangered orchid
- Wild orchids of "Alta Murgia" (Apulia - Southern Italy)
- Wild orchid of Japan - Flavon's art gallery
- Wild orchids - South Indian orchids
- Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 7, May 2006 [and more or less continuously updated since].