Joseph's spider orchid

Caladenia polychroma is a terrestrial, perennial, deciduous, herb with an underground tuber and which often grows in clumps. It has a single erect, hairy leaf, 70–120 mm (3–5 in) long and about 4 mm (0.2 in) wide. One or two creamy variably red, pink, yellow and white flowers 100–150 mm (4–6 in) long and 80–120 mm (3–5 in) wide are borne on a stalk 200–300 mm (8–10 in) tall. The sepals and petals have long, thin, drooping, thread-like ends. The dorsal sepal is erect, 45–100 mm (2–4 in) long and 2–3 mm (0.08–0.1 in) wide. The lateral sepals are 45–100 mm (2–4 in) long and 3–4 mm (0.1–0.2 in) wide and curve stiffly downwards. The petals are 45–90 mm (2–4 in) long, 2–3 mm (0.08–0.1 in) wide and arranged like the lateral sepals. The labellum is 10–17 mm (0.4–0.7 in) long, 10–13 mm (0.4–0.5 in) wide and cream-coloured to yellow with red lines, spots and blotches. The sides of the labellum have short, blunt teeth and the tip is curled under. There are two rows of anvil-shaped, cream-coloured calli along the mid-line of the labellum. Flowering occurs from September to October.

Joseph's spider orchid occurs between Frankland and the Fitzgerald River National Park in the Avon Wheatbelt, Esperance Plains, Jarrah Forest and Mallee biogeographic regions but is most common between Cranbrook and Kojonup. It grows near seasonally wet areas and drainage lines.