Orchids, Tropicals

Orchids (Orchidaceae family) are among the largest and most diverse of the flowering plant (angiospermae) families, with over 800 described genera and 25,000 (some sources give 30,000) species, and another 100,000 + hybrids and cultivars produced by horticulturalists. more...

The Kew World Checklist of Orchids includes about 24,000 accepted species. About 800 new species are added each year. Orchids, through their floral complexity and their interactions with pollinators and their symbiosis with mycorrhizae, are considered by some, along with the grasses, to be examples of the most complex floral evolution known.

Orchids get their name from the Greek orchis, meaning 'testicle', from the appearance of subterranean tuberoids in some terrestrial species. The word 'orchis' was first used by Theophrastos (372/371 - 287/286 BC), in his book "De historia plantarum" (The natural history of plants). He was a student of Aristotle and is considered the father of botany and ecology.

All orchid species are protected for the purposes of international commerce under CITES as potentially threatened or endangered in their natural habitat, with most species listed under Appendix II. A number of species and genera are afforded protection under Appendix I, including all of Paphiopedilum and all of Phragmipedium. Many other species are protected by both international and national legislation, while hybrids are specifically exempted.

General description

These monocotyledonous plants are cosmopolitan in distribution, occurring in every habitat, except Antarctica and deserts. The great majority are to be found in the tropics, mostly Asia, South America and Central America. They are to be 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 :

• Eurasia : 40 to 60 genera
• North America : 20 to 30 genera
• tropical America : 300 to 350 genera
• tropical Africa : 125 to 150 genera
• tropical Asia : 250 to 300 genera
• Oceania : 50 to 70 genera

Orchids can be grouped according to the way they retrieve nutrients:

• A majority of species are perennial epiphytes; they are found in tropical moist broadleaf forests or mountains and subtropics. These are anchored on other plants, mostly trees, sometimes shrubs. Note that they are not parasites.
• A few are lithophytes, similar to epiphytes but growing on rocks, not plants.
• Others are terrestrial plants, obtaining their nutrients from the soil. This group includes nearly all temperate orchids.
• Some lack chlorophyll and are epiparasites, also referred to as "myco-heterotrophs" (formerly wrongly called saprophytes). These achlorophyllous orchids have an ectomycorrhizal relationship, i.e. they are completely dependent for nutrients on soil fungi that feed on decaying plant matter (usually fallen leaves). A typical example is the Bird's-nest Orchid (Neottia nidus-avis) or the Californian orchid Corallorhiza maculata.

All orchids have these five basic features:

Read more at Wikipedia.org