Age and beauty: kin to both irises and onions, orchids have a long history and a large repertoire of enticing tricks.

Ask a glamorous older woman her age and the secret to her beauty, and you're likely to get a Mona Lisa smile and a deft change of subject. Until recently, botanists have met with similar impenetrability when asking these questions about orchids, the glamour queens of the plant kingdom.

The orchid family--Orchidaceae--has a greater wealth of species than any other plant family on Earth: naturally occurring species number around 30,000, and artificially created hybrids in the tens of thousands. Most of them are epiphytes, growing with their roots not in soil but instead harmlessly clasping tree branches high in the forest canopy. A few are parasites; lacking ...