Pterostylis ventricosa

Pterostylis ventricosa is a terrestrial, perennial, deciduous, herb with an underground tuber and when not flowering, a rosette of four to nine dark green, egg-shaped leaves which lie flat on the ground. Each leaf is 3–12 mm (0.1–0.5 in) long and 3–6 mm (0.1–0.2 in) wide. Flowering plants have up to six well-spaced flowers 10–13 mm (0.4–0.5 in) long and about 5 mm (0.2 in) wide borne on a thin, wiry spike 80–300 mm (3–10 in) high. One or two leaf rosettes are arranged on the side of the flowering spike. The flowers are green and white, swollen at the base and taper towards a bright reddish-brown tip. The dorsal sepal and petals are fused, forming a hood or "galea" over the column. The dorsal sepal is erect near the base but then curves forward and is 13–16 mm (0.5–0.6 in) long and 5–8 mm (0.2–0.3 in) wide. The petals are slightly longer than the dorsal sepal. The lateral sepals are erect, held closely against the galea with thread-like tips about 3mm long reaching just past the top of the galea. The labellum is about 5 mm (0.2 in) long, 2 mm (0.08 in) wide, dark brown and white, curved and barely visible above the sinus.[3][4]

This greenhood was first formally described in 2008 by D.L.Jones who gave it the name Speculantha ventricosa and published the description in The Orchadian.[5] In 2010, Gary Backhouse changed the name to Pterostylis ventricosa.[1] The specific epithet (ventricosa) is a Latin word meaning "pot-bellied" or "bulging".[6]

The tiny greenhood mostly grows in tall forest with a dense understorey, but sometimes in disturbed areas, including roadsides. It occurs near Nowra, Tallong and Mittagong.[3][4]

Pterostylis ventricosa is classed as "critically endangered" under the New South Wales Threatened Species Conservation Act. The main threats to the species are land clearing, disturbance by off-road vehicles, grazing by livestock and illegal collection.[3][4]