Overview
The Spoon-lipped Greenhood (Pterostylis spathulata) is a widespread and architecturally fascinating terrestrial orchid found across the semi-arid woodlands and granite outcrops of Western Australia. Belonging to the rufa greenhood group, it features a translucent, green-and-brown striped hood (galea) and an extraordinarily sensitive, spoon-shaped irritable labellum engineered as a dynamic insect-trapping mechanism. Flowering from June through October, it is remarkably resilient to seasonal moisture fluctuations.
Biology and Physical Characteristics
Pterostylis spathulata develops an initial basal rosette of three to six oval, blue-green leaves that typically wither by the time the flowering stem matures. The stem reaches up to 30 centimeters in height, bearing two to eight nodding, translucent green flowers adorned with rich rufous-brown or brownish-orange stripes. The dorsal sepal and petals fuse to form a protective helmet (galea) ending in a short downcurved beak. Inside lies the irritable labellum, which is distinctly spoon-shaped (spathulate), fleshy, and lined with fine microscopic tactile bristles.
Behavior and Ecology
The pollination mechanism of Pterostylis spathulata is a marvel of biomechanical precision. Small fungus gnats and sciarid flies are attracted to the flower by faint chemical secretions mimicking fungal brood sites. When an insect lands on the sensitive spoon-shaped labellum, a sudden mechanical reflex triggers the appendage to snap upward in a fraction of a second, trapping the gnat within the interior column chamber. The only route of escape forces the insect to squeeze past the stigma and pollinia, ensuring efficient pollen transfer.
Conservation and Human Impact
Pterostylis spathulata is ranked as Least Concern, being one of the most widely distributed inland greenhoods in Western Australia. It persists in diverse habitats ranging from coastal dunes to semi-arid Goldfields woodlands. Populations within agricultural belts benefit from the protection of granite inselberg nature reserves, where shallow soils discourage commercial clearing and provide natural fire refugia.
Interesting Factoid
The sensitive spoon-shaped labellum acts as a spring-loaded trapdoor: once triggered by a landing gnat, it remains closed for several minutes before resetting itself, ensuring the insect cannot escape without crawling through the reproductive column.
Last updated: October 2026