Thelymitra stellata (also known as Star Sun-orchid) is listed as Endangered under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) and as Declared rare Flora under the Wildlife Conservation Act 1950.
The main identified threats to Thelymitra stellata are fire during the growing season; browsing by feral rabbits (Oryctolagus cuniculus); broad scale vegetation clearing; and increasing fragmentation of habitat. The main potential threats to the species include invasion by exotic weeds; recreational activities; road widening activities; and gravel extraction.
Thelymitra stellata is a terrestrial orchid growing to 25 cm high on a robust stem. It has up to six symmetrical flowers, 2.5–3 cm in diameter. The flowers are usually golden brown but may be yellow with orange stripes on the sepals and petals. Star Sun-orchid flowers form late September to November. At the base of the stem there is a single lily-like leaf, up to 9 cm long and 4 cm wide. The leaf is usually shrivelled by the time of flowering and the plant dies back below ground level after seed set. It is closely-related to T. jacksonii and T. fuscolutea but differs in having smaller, lighter coloured flowers, an earlier flowering period and a more northerly range of distribution. Thelymitra flowers remain closed at night or on cool, cloudy days, opening only in warm, sunny weather.
Star Sun-orchid is endemic to Western Australia where it is uncommon but occurs over a wide area, and is known from 23 populations between Three Springs and Pinjarra, with a single disjunct occurrence near Dumbleyung. The populations are small, most numbering fewer than 10 plants. Star Sun-orchid is conserved in Mt Lesueur National Park and Coomallo Nature Reserve but some populations occur on private land or along roadsides. The species grows in gravelly loam among low heath and scrub in Eucalyptus marginata and E. wandoo woodland, and in low heath on lateritic hill tops.
Information Source: Government of Australia, Department of Environment and Department of Parks and Wildlife Western Australia