Caladenia bicalliata subsp. cleistogama, commonly known as the shy limestone spider orchid or sandhill spider orchid, is a plant in the orchid family Orchidaceae and is native to the south-west of Western Australia. It has a single erect, hairy leaf and one or two cream-coloured flowers which are smaller than those in subspecies bacalliata .
Caladenia bicalliata subsp. cleistogama is a terrestrial, perennial, deciduous, herb with an underground tuber and which occurs singly or in small clumps. It has a single erect, very hairy, linear to lance-shaped leaf, NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide. The inflorescence is a raceme, NaNsigfig=1NaNsigfig=1 high with one or two flowers, each flower about 25sigfig=1NaNsigfig=1 long and 10sigfig=1NaNsigfig=1 wide. The dorsal sepal abruptly narrows about one-third of its length from the base. The lateral sepals and petals are much shorter than those of subspecies bicalliata, lack reddish-brown tips and are a paler greenish-cream colour. The labellum is white with red spots and a serrated edge and has two rows of white-tipped calli along its centre. Flowering occurs from August to early September, however the flowers only rarely open fully.[1] [2]
Caladenia bicalliata was first formally described by Richard Rogers in 1909.[3] In 2001 Stephen Hopper and Andrew Brown described two subspecies, including subspecies cleistogama and the description of the two subspecies was published in Nuytsia.[4] The specific epithet (cleistogama) is from the Latin cleistogamus (fertilised within the unopened flower), referring to the self-pollinating habit of this subspecies.
Shy limestone spider orchid occurs in a narrow coastal strip, growing on consolidated sand dunes between William Bay National Park and Cape Arid National Park in the Esperance Plains and Warren biogeographic regions.[5]
Caladenia bicalliata subsp. cleistogama is classified as "not threatened" by the Western Australian Government Department of Parks and Wildlife.