Caladenia interjacens, commonly known as the Walpole spider orchid, is a species of orchid endemic to the south-west of Western Australia. It has a single, hairy leaf and one or two pale pink and white flowers which lack the red tip on the labellum common to many other similar caladenias.
Caladenia interjacens is a terrestrial, perennial, deciduous, herb with an underground tuber and a single erect, hairy leaf, long and wide. One or two white flowers with pinkish markings and long and wide are borne on a stalk tall. The sepals have pinkish-grey to brownish, club-like glandular tips long. The sepal is erect, long and wide. The sepals are long, wide and turn stiffly downwards. The petals are long and wide and spread nearly horizontally. The labellum is long and wide and pinkish-white with the tip rolled under and lacking a red tip. The sides of the labellum have pinkish teeth up to long and four to six rows of pinkish to deep red calli up to long in the centre. Flowering occurs from September to late October.
Caladenia interjacens was first described in 2001 by Stephen Hopper and Andrew Phillip Brown from a specimen collected in the Walpole-Nornalup National Park and the description was published in Nuytsia. The specific epithet (interjacens) is a Latin word meaning "intervening" or "coming between" referring to the characteristics of the flowers of this species being intermediate between those of Caladenia longicauda and C. huegelii.
The Walpole spider orchid occurs between Walpole and West Cliff Point in the Jarrah Forest and Warren biogeographic regions where it grows in woodland and in low coastal heath.
Caladenia interjacens is classified as "Priority Four" by the Government of Western Australia Department of Parks and Wildlife, meaning that is rare or near threatened.