Thelymitra arenaria, commonly called the forest sun orchid, is a species of orchid that is endemic to south-eastern Australia. It has a single long, narrow leaf and up to sixteen purplish self-pollinating flowers which only open on hot days.
Thelymitra arenaria is a tuberous, perennial herb with a single leathery, channelled, dark green linear to lance-shaped leaf NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide with a purplish base. Between two and sixteen purplish flowers NaNsigfig=1NaNsigfig=1 wide are borne on a flowering stem NaNsigfig=1NaNsigfig=1 tall. There are usually and two bracts on the flowering stem. The sepals and petals are NaNsigfig=1NaNsigfig=1 long and NaNsigfig=1NaNsigfig=1 wide. The column is pale blue with dark blue streaks, NaNsigfig=2NaNsigfig=2 long and NaNsigfig=2NaNsigfig=2 wide. The lobe on the top of the anther is dark brown with a yellow tip and gently curved. The side lobes curve upwards and have dense, hairbrush-like tufts of white hairs. The flowers are self-pollinating and only open on warm to hot, humid days. Flowering occurs from October to December.[1] [2] [3]
Thelymitra arenaria was first formally described in 1840 by John Lindley from a specimen collected in Tasmania and the description was published in his book The genera and species of Orchidaceous plants.[4] The specific epithet (arenaria) is a Latin word meaning "of sand" or "sandy".[5]
The forest sun orchid is widespread and common within most of its range. It grows in a wide range of habitats from grassland to forest and is found in southern New South Wales, the Australian Capital Territory, in the southern half of Victoria, in south-eastern South Australia and in Tasmania.