It has a single tube-shaped leaf and up to fifteen greenish and pinkish-brown flowers with a whitish labellum.

There is a raised, claw-like, yellowish brown callus in the centre of the labellum and extending almost to its tip.

[2] Prasophyllum crassum was first formally described in 2017 by David Jones and Robert Bates and the description was published in Australian Orchid Review from a specimen collected in the Desert Camp Conservation Park.

[1] The specific epithet (crassum) is a Latin word meaning "thick", "fat" or "stout",[3] referring to the fleshy texture of this orchid.

[2] This leek orchid mostly grows in low lying, winter wet areas in the Big Heath Conservation Park and between Kingston, Mundulla and Frances.