Thelymitra is a genus of about 80 species of terrestrial tuberous plants in the Orchidaceae family distributed throughout Australia, New Zealand and islands to the north of Australia. They are known as "sun orchids" because the colorful flowers of most species only open fully on warm, sunny days, with the desert species requiring more heat than those from temperate areas. Like many bulbs, they bloom better in the year after a fire.
The number of flowers per stem is variable. Some, such as the scented sun orchid, will have up to 30 flowers open on a single stem. Most Thelymitra are native to the southwest of Australia with species found in almost every habitat. Unlike other Australian orchids, this genus has sepals and petals nearly equal in length, with the lip similar to and spreading with them. They have a solitary leaf that is usually elongated and channeled. Species are identified by their color and their column.
Peter Bernhardt and Retha Meier studied the pollination of some of these species and published an article entitled Sun Orchids, Successful and Immoral (PDF) in For People and Plants, the magazine of the Friends of the Kings Park. We are linking to this article with their permission.
The Species Orchid Society of Western Australia hosts a lot of information online about Australian orchids here, including an overview of the genus Thelymitra here. The late Ron Heberle was a passionate advocate for Australian terrestrial orchids. Some of his photographs are reproduced here, with permission.
The Australian terrestrial orchids are notoriously challenging to grow, although some enthusiasts are starting to achieve success by cultivating the symbiotic fungus that many of the orchids require in order to grow. Very careful fertilization is required to keep the fungus and orchid in balance. There's a good discussion of the relationship here.
For more photos and information about the species select the appropriate wiki page or click a name in the table below: