Prasophyllum stygium, commonly known as the elfin leek orchid, is a species of orchid endemic to Victoria. It has a single tube-shaped leaf and up to twenty greenish-brown flowers with a white labellum. It is a recently described plant, previously included with P. fitzgeraldii, but distinguished from that species by its greenish-brown flowers with their white labellum and narrower brown callus. It is only known from a single population of about thirty plants.
Prasophyllum stygium is a terrestrial, perennial, deciduous, herb with an underground tuber and a single tube-shaped, shiny, pale green leaf which is NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide at its maroon base. Between eight and twenty greenish-brown flowers are arranged along a flowering spike NaNsigfig=1NaNsigfig=1 long, reaching to a height of NaNsigfig=1NaNsigfig=1. The flowers are NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide. As with others in the genus, the flowers are inverted so that the labellum is above the column rather than below it. The dorsal sepal is lance-shaped to egg-shaped, NaNsigfig=2NaNsigfig=2 long and about 2.5sigfig=1NaNsigfig=1 wide. The lateral sepals are egg-shaped to lance-shaped, NaNsigfig=1NaNsigfig=1 long, NaNsigfig=1NaNsigfig=1 wide and free from each other. The petals are brownish-green with whitish edges, linear to oblong, NaNsigfig=2NaNsigfig=2 long and NaNsigfig=1NaNsigfig=1 wide. The labellum is white, lance-shaped to egg-shaped, NaNsigfig=2NaNsigfig=2 long, NaNsigfig=1NaNsigfig=1 wide and turns sharply upward at 90° about half-way along, reaching the lateral sepals. The edges of the upturned part are wavy or crinkled with hair-like papillae. There is a raised, oblong, coffee-coloured callus in the centre of the labellum and extending almost to its tip. Flowering occurs in late October or early November and only lasts a few days.[1] [2]
Prasophyllum stygium was first formally described in 2017 by David Jones and Dean Rouse and the description was published in Australian Orchid Review from a specimen collected in the Deep Lead Nature Conservation Reserve near Stawell.[3] The specific epithet (stygium) is a Latin word meaning "stygian" after the mythological river Styx,[4] referring to the type location, a former mining area where gold was extracted from buried river beds.
The elfin leek orchid is only known from about thirty plants growing in forest at the type location.