Overview
The Painted Greenhood (Pterostylis picta) is an ornate terrestrial orchid that decorates the mossy aprons of ancient granite monadnocks across inland Western Australia. Renowned for its richly painted galea hood, which features vibrant longitudinal stripes of deep chocolate-brown, rich mahogany, and bright emerald-green, this resilient geophyte braves the semi-arid interior with remarkable biological ingenuity.
Biology and Physical Characteristics
Pterostylis picta produces a rosette of five to ten ovate green leaves that encircle the base of the stem during autumn, often withering as the flowering scape matures in early spring. The upright flowering stem reaches 10 to 25 centimeters, presenting a solitary semi-erect hooded flower. The galea is arched gracefully forward, composed of fused dorsal sepals and petals with translucent windowed interspaces between bold crimson-brown stripes. The lateral sepals are erect with slender filamentous tips, and the interior labellum is narrow, curved, and hinged upon a sensitive irritable claw.
Behavior and Ecology
Flowering from July to October, Pterostylis picta functions as an insect trapdoor system. Small male fungus gnats are lured by subtle scents mimicking female gnat pheromones. When a gnat alights on the labellum, the irritable hinge instantly snaps upward, sealing the insect inside the hooded galea against the column. Trapped in darkness, the gnat crawls toward the only illuminated translucent light cells at the apex of the column, squeezing past the stigma and pollinia to effect pollination before being released as the labellum relaxes.
Conservation and Human Impact
Evaluated as Least Concern, Pterostylis picta is well protected across numerous granite inselberg reserves and national parks throughout the Wheatbelt and interior, including Peak Charles and Boyagin Rock. Key conservation measures include safeguarding fragile moss mats on granite rocks from tourist trampling and managing feral goat grazing.
Interesting Factoid
The translucent, colorless cells in the back of the hooded flower act like natural skylights, guiding imprisoned fungus gnats precisely through the escape tunnel where pollination occurs.
Last updated: October 2026