Pterostylis dubia

Pterostylis dubia, commonly known as the blue-tongued greenhood, is a plant in the orchid family Orchidaceae and is endemic to Tasmania. It has a rosette of fleshy leaves at its base and a dark green and white flower with narrow petals and a dark blue-green labellum.

Description
Pterostylis dubia, is a terrestrial, perennial, deciduous, herb with an underground tuber. It has a rosette of leaves which are 15-60 mm long, 8-20 mm wide and have a stalk. Flowering plant have a single dark green and white flower 20-26 mm long and 9-12 mm wide is borne on a flowering stem 80-200 mm tall with stalkless stem leaves. The dorsal sepal and petals are joined, forming a hood called the "galea" over the column. The petals are not flared and are similar in length to the dorsal sepal which ends in a point. There is a wide gap at each side of the flower between the galea and the lateral sepals. The lateral sepals are erect and have a tapering tip, 14-22 mm long, only slightly taller than the galea and there is a notch in the bulging sinus between them. The labellum is 13-17 mm long, about 3 mm wide, dark bluish-green, curved and protrudes prominently above the sinus. Flowering occurs from November to January.

Taxonomy and naming
Pterostylis dubia was first formally described in 1810 by Robert Brown and the description was published in Prodromus Florae Novae Hollandiae et Insulae Van Diemen. The specific epithet (dubia) is a Latin word meaning "wavering", "uncertain" or "doubtful".

Distribution and habitat
The blue-tongued greenhood grows in wet forest at altitudes above 500 m in central and southern Tasmania.