The Orchidaceae is among the largest families of flowering plants. For many, an introduction to the orchid family begins with the lady's-slipper orchid that grows in North America and other temperate climates. Here, Cypripedium x columbianum growing at the edge of a marsh. Orchids grow in all terrestrial ecosystems, except in the North and South Poles, but their greatest diversity is found in the tropics.
Terrestrial orchids predominate in temperate habitats, epiphytes in tropical habitats.
Orchids may be divided into two fundamental types based on growth habit. Sympodial orchids, such as cattleyas and paphiopedilums, are characterized by individual shoots with limited growth. Creeping stems called rhizomes are made of basal portions of successive shoots. Buds give rise to new shoots, each developing to maturity and flowering. Shoots of monopodial orchids, on the other hand, have unlimited growth, each continuing to produce leaves from the stem apex and inflorescences from between the leaves.