It has a single hollow, onion-like leaf and up to fifty small green or yellowish-green, scented flowers.

Flowering occurs from November to January and is stimulated by fire the previous summer.

[3][4][5][6] Microtis rara was first formally described in 1810 by Robert Brown and the description was published in Prodromus Florae Novae Hollandiae et Insulae Van Diemen.

[1][7] The specific epithet (rara) is a Latin word meaning "scarce", "scattered" or "dispersed".

[5][9] The scented onion orchid grows swamps and wet forests and is widespread but not common, occurring in all states but not the Northern Territory.