Thelymitra polychroma, commonly called the rainbow sun orchid, is a species of orchid that is endemic to Tasmania. It has a single narrow, fleshy leaf and up to four blue and mauve flowers with darker veins. It grows in windswept heath and swampy areas and the flowers are self-pollinated.
Thelymitra polychroma is a tuberous, perennial herb with a single fleshy, channelled, linear leaf NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide. Up to four blue and mauve flowers with darker veins and a few small spots, NaNsigfig=1NaNsigfig=1 wide are arranged on a flowering stem NaNsigfig=1NaNsigfig=1 tall. The sepals and petals are NaNsigfig=1NaNsigfig=1 long and about 5sigfig=1NaNsigfig=1 wide. The column is pink and purple with a shiny pink base and blue edges, about 5sigfig=2NaNsigfig=2 long and 2.5sigfig=1NaNsigfig=1 wide. The lobe on the top of the anther is brown with a yellow tip and wrinkled back. The side lobes have dense, mop-like tufts of cream-coloured hairs. Flowering occurs in November and December but the flowers are self-pollinated and only open on hot days. Flowering is more prolific after fire the previous summer.[1] [2]
Thelymitra polychroma was first formally described in 1998 by David Jones and Mark Alwin Clements and the description was published in Australian Orchid Research.[3] The specific epithet (polychroma) is derived from the Greek words polys meaning “many"[4] and chroma meaning "colour", referring to the colours on the column.
The rainbow sun orchid grows in windswept coastal and near coastal heath in western Tasmania.