The sepals and petals are egg-shaped to triangular, spread widely apart from each other and about 1.5 mm (0.059 in) long.

[2][4] The southern green fairy orchid was first formally described in 1839 by Allan Cunningham who gave it the name Dendrobium complanatum and published the description in Edwards's Botanical Register.

[7][8] Oberonia complanata grows on trees and rocks in rainforest between Gympie in Queensland and Coffs Harbour in New South Wales.

[2][4] This orchid is classed as "endangered" in New South Wales under the Biodiversity Conservation Act 2016.

The main threats to the species are land clearing, habitat degradation and illegal collecting.