It is similar to P. pyriforme from mainland Australia but lacks that species' white to pinkish labellum.

Flowering occurs from October to December and is strongly promoted by fires the previous summer.

[2][3] Prasophyllum rostratum was first formally described in 1840 by John Lindley and the description was published in The Genera and Species of Orchidaceous Plants.

[1] The specific epithet (rostratum) is a Latin word meaning "beaked" or "curved",[4] referring to the tail-like tip of the labellum.

[3] The slaty leek orchid grows in a range of heath and sedge habitats, mainly in the north and north-west of Tasmania.