Overview
The Rough Greenhood (Pterostylis scabra) is a winter-blooming terrestrial orchid widely distributed across the granite outcrops and rocky landscapes of southern Western Australia. Characterized by its upright, translucent green hood (galea) boldly striped with emerald and reddish-brown bands, this resilient geophyte braves the wettest and coldest months of the year to complete its reproductive cycle.
Biology and Physical Characteristics
Pterostylis scabra exhibits dimorphic vegetative growth: non-flowering plants form a flat ground-hugging rosette of ovate leaves, whereas flowering stems produce smaller, stem-clasping bracts beneath a solitary terminal flower. The galea is formed by the fusion of the dorsal sepal and petals, creating a translucent, arched helmet. The lateral sepals are erect, tapering into fine, upright points that project well above the galea. The microscopic scabrid surface texture along its flowering stem provides the species with its scientific and common names.
Behavior and Ecology
Flowering from May through August, Pterostylis scabra uses a touch-sensitive trapdoor mechanism to manipulate pollinators. Fungus gnats (Mycetophilidae) are attracted into the galea opening by alluring floral scent cues. Once inside, the insect steps onto the irritable, hinged labellum, which instantly snaps upward, trapping the gnat inside the column chamber. The gnat’s only exit route forces it through a narrow escape tunnel past the pollinia and stigma, ensuring successful pollen transfer before the trap resets.
Conservation and Human Impact
Pterostylis scabra is evaluated as Least Concern, being one of the most abundant and widespread greenhood orchids in south-western Australia. Robust populations flourish within protected national parks including Cape Le Grand, Stirling Range, and John Forrest National Parks. Protection of granite rock aprons from quarrying, excessive recreational foot traffic, and feral goat disturbance safeguards wild colonies.
Interesting Factoid
The sensitive labellum of the Rough Greenhood operates like a spring-loaded trapdoor; the moment a tiny fungus gnat steps on it, the lip triggers in a fraction of a second, sealing the insect inside the floral chamber until it crawls past the orchid’s pollen packets.
Last updated: October 2026