It has a single tubular, dark green leaf and up to thirty five scented, greenish-brown to brownish flowers and is only known from a few small populations in south-western Victoria.

[3][4] Prasophyllum viretrum was first formally described in 2006 by David Jones and Dean Rouse from a specimen collected at the Pretty Hill Flora Reserve, near Orford and the description was published in Australian Orchid Research.

[5] The specific epithet (viretrum) is derived from the Latin word viretum meaning "greensward", "sod" or "turf".

[4][6] This leek orchid grows in grassland in moist places and is only known from four or five populations near Warrnambool, Orford, Port Fairy and Mortlake in south-west of the state.

[3] Prasophyllum viretrum is listed as "critically endangered" under the Victorian Government Flora and Fauna Guarantee Act 1988.