Feature Article - Tasmania's native orchids
Feature article published in the Tasmanian Year Book, 2000 (cat. no. 1301.6)
Contributed by Hans Wapstra, Department of Primary Industries, Water and Environment
With 195 species, the orchids are a substantial family in the Tasmanian flora. About one third of them are endemic to the State, and close to half the endemics are rare or threatened. Many of the species we share with other south-eastern Australian States are also in a precarious position.
All but two of our orchids are terrestrial. The richest orchid habitats are dry sclerophyll woodlands and open forests, especially those on sandy soils with heathy and grassy understorey, coastal heathlands and native grasslands. Most orchids flower in spring to early summer, but any month of the year has at least one or two species in flower.
Until the early 1990s orchids were a little known group to all but a handful of specialists, mostly amateur botanists. Unlike most other vascular plants, orchids flower for just a few weeks, in some species only two or three days. The leaves of non-flowering plants are above ground for many months but are hidden among other vegetation, and in any case, are of little help in identifying the species. In addition there have been numerous taxonomic problems. For instance, plants known as the common spider orchid had been a botanical ‘catch-all’ for at least half a dozen species for well over a century, most of them very rare and with a restricted distribution. With all these difficulties, it is not surprising that orchids rarely appeared by name in botanical surveys, and that most information on abundance or rarity was fragmented.
This has now changed. Since 1992 systematic taxonomic studies and field surveys have been in progress. A comprehensive revision of the Tasmanian orchid flora was published in 1998 and included the recognition and formal description of nearly fifty new species. No less than twenty have been discovered since 1995 which were not just new in the taxonomic sense but species never seen before. In 1999 the book The Orchids of Tasmania was published, marking a turning point for Tasmanian orchid studies. The book has new identification keys, descriptions, distribution maps and colour photographs of every known species, enabling professional and amateur botanists to comprehend all our known species.
Perhaps the most exiting discoveries were on a golf course in the Midlands, where in one spring season three endangered orchids were found. One of these was the Gaping Leek Orchid (Prasophyllum correctum) previously known from one small and highly threatened colony in Victoria. Thousands of thriving plants were discovered in the golf course rough as a result of a wayward golf ball. The other two are the Pungent Leek Orchid (Prasophyllum olidum), an entirely new orchid with an overpowering smell, and the Black-tipped Spider Orchid (Caladenia anthracina), a native grassland species known from just a few plants in four Midland localities. Management measures by the golf club are now an excellent example of how landowners can contribute to conservation of rare plants or habitats.
Remnant native grasslands and grassy woodlands, like the Midlands golf course, are a haven for a large number of threatened plants, including about 20 orchids. Some of these are currently known from just one or two localities, and often only a handful of plants. Almost half of the native grasslands present at the time of settlement have disappeared, most of them in more recent times due to pasture conversion and improvement, by ploughing, application of fertilisers and sowing with introduced pasture species. Orchids in particular have been very sensitive to the use of fertilisers, which are taken up preferentially to levels toxic to the plants.
Effective management of rare habitats and species will increasingly rely on the understanding and goodwill of landowners.