Caladenia williamsiae

Caladenia williamsiae is a terrestrial, perennial, deciduous, herb with an underground tuber and a single erect, hairy leaf, 70–90 mm long and 15–18 mm wide. One or two greenish-yellow flowers with red markings, and about 40 mm long and 30 mm wide are borne on a stalk 150–200 mm high. The sepals have reddish, club-like glandular tips 3–4 mm long. The dorsal sepal is erect near the base, then curves forward and is 15–20 mm long and about 1 mm wide. The lateral sepals and petals are 15–20 mm long, about 2 mm wide and horizontal near their bases, then curve downwards. The labellum is 6–8 mm long, 3–4 mm wide and yellowish green with a red tip. The sides of the labellum have narrow red or cream-coloured teeth up to 3 mm long, the tip of the labellum curls downward and there are four rows of dark red calli up to 1 mm long, along the mid-line. Flowering occurs from August to September.[2][3][4][5][6]

Caladenia williamsiae was first formally described in 2001 by Stephen Hopper and Andrew Phillip Brown from a specimen collected near Brookton and the description was published in Nuytsia.[1] The specific epithet (williamsiae) honours Judy Williams who discovered this species in 2000.[3]

Judy's spider orchid is only known from near Brookton in the Avon Wheatbelt biogeographic region where it grows under wandoo and in dense shrubland.[2][3][4][5][7]

Caladenia williamsiae is classified as "Threatened Flora (Declared Rare Flora — Extant)" by the Western Australian Government Department of Parks and Wildlife[7] and as "Endangered" (EN) under the Australian Government Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). The main threat to the species is grazing by kangaroos.[6]