All orchids belong to the Orchid Family, Orchidaceae (or-Kid-ACE-ee-ee). Orchids are divided into two basic growth types: monopodial and sympodial. Monopodial orchids have a central stem which grows continuously from the tip. Flowers are produced from the stem between the leaves, usually alternately from side to side. Phalaenopsis orchids are a good example. Sympodial orchids, such as cattleyas, laelias and paphiopedilums, possess a rhizome which sends out a shoot. This develops into a stem and leaves and eventually produces flowers. In time, from the base of this growth, a new shoot develops and so on in a continuous cycle. The buds are often, though not always, protected by a sheath.

The mid section of stems of sympodial orchids are often expanded into water-storage organs called pseudobulbs. These vary greatly in size and shape, ranging from tall and pencil-thin to bulbous and onion-like. The leaves vary too, some being soft and folded like a fan, others thick and leathery. The roots of epiphytic orchids have an outer layer or corky cells called velamen, which protects the thin, living cortex within. These adaptations allow orchids to absorb water and nutrients rapidly from raindrops, but protect roots, stems and leaves from water loss during dry periods. Most orchids are adapted to conserve water and should be cared for as such.