Caladenia ultima

Caladenia ultima is a terrestrial, perennial, deciduous, herb with an underground tuber and a single erect, hairy leaf, 60–150 mm long and 2–4 mm wide. Up to three creamy yellow or pale lemon-yellow flowers 80–110 mm long and 60–90 mm wide are borne on a stalk 150–250 mm tall. The sepals have long, brown, thread-like tips. The dorsal sepal is erect, 60–80 mm long and about 2 mm wide. The lateral sepals are 60–80 mm long, about 3 mm wide and turn stiffly downwards. The petals are 50–75 mm long, 2–3 mm wide and turn slightly upwards. The labellum is 12–15 mm long, 7–9 mm wide and creamy-white with red stripes and blotches with the tip curled downwards. The sides of the labellum are serrated and there are two rows of anvil-shaped, white or creamy-white calli along the mid-line. Flowering occurs from late October to early December, making it one of the last spider orchids to flower each year.[2][3][4]

Caladenia ultima was first formally described in 2001 by Stephen Hopper and Andrew Phillip Brown from a specimen collected in the Stirling Range and the description was published in Nuytsia.[1] The specific epithet (ultima) is a Latin word meaning "farthest" or "last"[5] referring to the late flowering of this orchid.[3]

The late spider orchid is found in the Stirling Range National Park and Mount Barker area in the Esperance Plains and Jarrah Forest biogeographic regions where it grows in low-lying areas that are wet in winter.[2][3][4][6]

Caladenia ultima is classified as "Priority Two" by the Western Australian Government Department of Parks and Wildlife,[6] meaning that it is poorly known and known from only one or a few locations.[7]