Orchids with blue flowers are rare in the orchid family. Australia has several terrestrial genera which can have flowers with this rare colour. These include Thelymitra and Cyanicula.
Cyanicula sericea is a common species that grows in the high rainfall areas between Esperance and Jurien Bay, south-west Western Australia. It grows in a variety of habitats that include eucalypt forests, coastal Banksia woodland and granite outcrops.
Plants are usually found growing exposed to bright light. The plant produces a single soft silky-hairy leaf from an underground tuber and the upright inflorescence can bear up to 3 (rarely 4) flowers. Its flowers face the sky. I have only ever seen them with a single flower. Variable in colour, the blooms may be blue to violet or rarely white.
This species was first described as Caladenia sericea. With the help of molecular studies, Stephen Hopper and Andrew Brown separated into its own genus Cyanicula [comprising 11 species] in 2000.
Cyanicula species are similar to Thelymitra in that they are usually temperature sensitive, requiring warm weather to open. The flowers tend to partially close during cool, cloudy weather - unlike other Caladenia.
The World Checklist of Selected Plant Families recognised Cyanicula for several years before reverting back to including Cyanicula as a synonym of Caladenia.
I prefer to recognise Cyanicula as distinct.
Reference: Brown, A., Dixon, K., French C. & G. Brockman. (2013) Field Guide to the Orchids of Western Australia. Simon Nevill Publications, York, Western Australia.
''Caladenia sericea'', commonly known as the silky blue orchid, is a plant in the orchid family Orchidaceae and is endemic to the south-west of Western Australia. It is a common orchid in the high rainfall areas of the state and has a single, broad, silky leaf and up to four blue-mauve flowers.