Pterostylis crassicaulis, commonly known as the alpine swan greenhood, is a plant in the orchid family Orchidaceae and is endemic to south-eastern Australia. It has a rosette of leaves and up to 18 bluish-green and white flowers with dark green stripes. The flowers have a labellum with a dark green, beak-like appendage. It is similar to P. cycnocephala but is more robust and grows at higher altitudes.
Pterostylis crassicaulis, is a terrestrial, perennial, deciduous, herb with an underground tuber. It has a rosette of between five and eight crowded, dark green leaves at the base of the flowering spike, each leaf NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide. Between 5 and 18 shiny bluish-green and white flowers with dark green lines and NaNsigfig=2NaNsigfig=2 long are borne on a flowering spike up to 300sigfig=1NaNsigfig=1 tall. Four to six stem leaves are wrapped loosely around the flowering spike. The dorsal sepal and petals form a hood or "galea" over the column. The dorsal sepal is curved forwards with the sides turned down. The lateral sepals turn downwards, are NaNsigfig=1NaNsigfig=1 long and wide, dished and joined near their bases. The labellum is oblong to egg-shaped, about NaNsigfig=1NaNsigfig=1 long and wide, pale green with a dark green, beak-like appendage pointing forward at its base. Flowering occurs from December to January.[1]
The alpine swan greenhood was first formally described in 2008 by David Jones and Mark Clements and given the name Hymenochilus crassicaulis. The description was published in The Orchadian from a specimen collected in the Kosciuszko National Park.[2] In 2010, Gary Backhouse changed the name to Pterostylis crassicaulis, publishing the change in The Victorian Naturalist.[3] The specific epithet (crassicaulis) is derived from the Latin words crassus meaning "thick", "fat" or "stout"[4] and caulis meaning "stalk" or "stem".
The alpine swan greenhood grows in alpine and subalpine grasslands and herbfields in eastern Victoria and on the Southern Tablelands of New South Wales.[5]