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ORCHID
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Orchids comprise about 7% of all flowering plants. Some taxonomists recognize as many as 35,000 species in 1,000 genera. Other taxonomists, however, recognize only about 20,000 species, but even this number ranks the Orchidaceae as the largest family of flowering plants. Orchids are perennials, with only one species, Zeuxine strateumatica, known to be an annual. They are also typically herbaceous, but some forms may be viny or somewhat woody. Orchid rootstock may become thickened to form overwintering tubers or pseudobulbs. From early classic times through the Middle Ages, terrestrial orchids with testiculate tubers were associated with human generative processes; in fact, the word orchid is derived from the Greek word for testicles, orchis.
Orchids are cosmopolitan, being found from the Arctic (Habenaria hyperborea) to the tropics and in almost every kind of habitat except desert. Most species, however, are tropical, and in the tropics most orchids are epiphytes, living upon other plants epiphytically but not parasitically. Temperate-zone orchids are mainly terrestrial, growing in soil. Some orchids are saprophytic, living on dead organic matter, such as leaf mold. A few grow completely underground.
Cultivation of orchids is an important worldwide greenhouse industry. Thousands of hybrids have been created. Most countries have societies devoted to orchid horticulture; the American Orchid Society has about 23,000 members.
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