Caladenia dilatata, commonly known as the green-comb spider-orchid[2] and as koolin by Aboriginal people of the Coranderrk area,[3] is species of flowering plant in the family Orchidaceae and is endemic to south-eastern Australia.

Caladenia dilatata is a terrestrial, perennial, deciduous, herb with an underground tuber and a single leaf which is 60–130 mm (2–5 in) long, 6–8 mm (0.2–0.3 in) wide with red spots near the base, but which is often dried by flowering time.

The sepals and petals have brown or yellowish, densely glandular, thread-like tips 5–15 mm (0.2–0.6 in) long.

The labellum is 13–17 mm (0.5–0.7 in) long and wide, green near the base, grading to white with a dark maroon tip.

[4][5] Caladenia dilatata was first formally described in 1810 by Robert Brown from a specimen collected at Port Dalrymple at the mouth of the Tamar River near Georgetown.

[9] With fewer competing plants, there is also believed to be an increase in moisture levels that can benefit Caladenia dilatata.