It has a single tubular, dark green leaf and up to twenty scented, yellowish-green to reddish-brown flowers.

It is similar to P. hectori, the only other species of Prasophyllum found in New Zealand, but is distinguished from it by its smaller size, fewer flowers and different habitat.

Prasophyllum colensoi is a terrestrial, perennial, deciduous, herb with an underground tuber and a single dark green, tube-shaped leaf 120–350 mm (5–10 in) long and 2–5 mm (0.08–0.2 in) wide with a whitish base.

[2][3] Prasophyllum colensoi was first formally described in 1853 by Joseph Dalton Hooker and the description was published in The botany of the Antarctic voyage of H.M. discovery ships Erebus and Terror in the Years 1839-1843.

This leek orchid is widespread on both the North and South Islands of New Zealand where it grows in grassland, between herbs and around the edge of bogs.