Overview
The Smooth Spider Orchid (Caladenia integra) is a remarkably distinctive terrestrial orchid endemic to the inland margins of southwest Western Australia. Unlike almost all other spider orchids, which feature conspicuously fringed or toothed labella, Caladenia integra possesses an entirely smooth, untoothed labellum margin—earning both its scientific name *integra* (entire) and common name.
Biology and Physical Characteristics
Caladenia integra produces an erect hairy scape arising from a solitary, narrow basal leaf. In mid to late spring (September to November), it bears one or two large, elegant blossoms. The sepals and petals are pale yellow-green with deep reddish-brown central stripes, terminating in thick, dark glandular clubs. The striking labellum is bright glossy green with a bold, velvety blackish-red apex, completely lacking teeth, comb fringes, or lateral serrations.
Behavior and Ecology
Despite its smooth labellum, Caladenia integra is an active practitioner of sexual deception. The swollen clubs at the tips of the sepals act as osmophores, releasing volatile chemical compounds that mimic the sex pheromone of a female thynnid wasp. Deceived male wasps land on the glossy, smooth labellum, which articulates on a claw-like hinge to swing the wasp into contact with the stigma and pollinia.
Conservation and Human Impact
Classified as Priority Four (Rare and Near Threatened) in Western Australia, Caladenia integra has a restricted distribution subject to historical clearing for agriculture. Significant populations are safeguarded within granite outcrop reserves around Kulin, Hyden, and Corrigin, where protection from grazing and weed encroachment supports viable wild colonies.
Interesting Factoid
Almost every spider orchid in Australia has fringed or combed edges along its labellum, making the completely smooth, polished rim of the Smooth Spider Orchid an extraordinary evolutionary departure.
Last updated: October 2026