Calochilus caesius, commonly known as the blue beard orchid, is a species of orchid endemic to the Northern Territory in Australia. It has a single leaf which is not present during flowering and up to five pale green, very short-lived flowers with a bluish-red "beard".
Calochilus caesius is a terrestrial, perennial, deciduous, herb with an underground tuber and a single leaf NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide but which is not present during flowering. Up to five pale green flowers NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide are borne on a thin, wiry flowering stem NaNsigfig=1NaNsigfig=1 tall. The dorsal sepal is NaNsigfig=2NaNsigfig=2 long and NaNsigfig=1NaNsigfig=1 wide. The lateral sepals are NaNsigfig=1NaNsigfig=1 long and about 4sigfig=1NaNsigfig=1 wide. The petals are NaNsigfig=2NaNsigfig=2 long and NaNsigfig=1NaNsigfig=1 wide. The labellum is flat, pale green and red, NaNsigfig=2NaNsigfig=2 long and NaNsigfig=1NaNsigfig=1 wide with bluish red hairs up to 2sigfig=1NaNsigfig=1 covering about three quarters of the labellum. The column lacks the sham "eyes" of some other beard orchids. Flowering occurs from December to February but each flower only lasts a few hours.[1]
Calochilus caesius was first formally described in 2004 by David Jones and the description was published in The Orchadian from specimens collected at Yarrawonga Swamp near Darwin.[2] The specific epithet (caesius) is a Latin word meaning "bluish gray".[3]
The blue beard orchid grows in swampy places with rushes and sedges in the far north of the Northern Territory including Garig Gunak Barlu National Park, Kakadu National Park and Melville Island.