Prasophyllum rostratum, commonly known as the slaty leek orchid, is a species of orchid endemic to Tasmania. It has a single tubular leaf and up to twenty five well-spaced, greenish-brown flowers. It is similar to P. pyriforme from mainland Australia but lacks that species' white to pinkish labellum.
Prasophyllum rostratum is a terrestrial, perennial, deciduous, herb with an underground tuber and a single tube-shaped leaf which is NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide. Between ten and twenty five greenish to greenish-brown flowers are loosely arranged along a flowering spike which is NaNsigfig=1NaNsigfig=1 long reaching to a height of NaNsigfig=1NaNsigfig=1. The flowers are NaNsigfig=2NaNsigfig=2 long and NaNsigfig=1NaNsigfig=1 wide and as with other leek orchids, are inverted so that the labellum is above the column rather than below it. The dorsal sepal is NaNsigfig=1NaNsigfig=1 long, about 4sigfig=1NaNsigfig=1 wide and the lateral sepals are NaNsigfig=1NaNsigfig=1 long, about 2sigfig=1NaNsigfig=1 wide, curve backwards and are free from each other. The petals are NaNsigfig=1NaNsigfig=1 long, about 1sigfig=1NaNsigfig=1 wide and curve forwards and slightly upwards. The labellum is NaNsigfig=1NaNsigfig=1 long, about 4sigfig=1NaNsigfig=1 wide and turns sharply upwards near its middle. There is a raised, fleshy, more or less bulbous callus in its centre. The labellum has a tail-like tip. Flowering occurs from October to December and is strongly promoted by fires the previous summer.[1] [2]
Prasophyllum rostratum was first formally described in 1840 by John Lindley and the description was published in The Genera and Species of Orchidaceous Plants.[3] The specific epithet (rostratum) is a Latin word meaning "beaked" or "curved",[4] referring to the tail-like tip of the labellum.
The slaty leek orchid grows in a range of heath and sedge habitats, mainly in the north and north-west of Tasmania.