Australia might never be thought of as one of the conventional centers of orchid diversity compared to South America and Asia; while Australia’s 1,500 plus orchid species representing only about 5.5% of the total number of orchid species, it is home to the world’s most diverse terrestrial or ground-growing orchids, about 80% of which are endemic and found nowhere else in the world!
Even rarer are the lithophytic orchids: orchids adapted to growing on rocks and stony cliffsides, of which the rock orchid (Dendrobium speciosum) is an outstanding representative. Not just your average cane Dendrobium, there are nine natural varieties of this species found only along the eastern coast of Australia. All varieties of this species are adapted to bright, almost full sun, low to moderate humidity, coarse, well-draining medium, and breezy areas with good airflow.
The variety we have at Gardens by the Bay, Dendrobium speciosum var. speciosum, also known as the Sydney rock orchid, is one of the most spectacular! Found between Sydney and Cann River, on rocks in open forest and cliff bases and very occasionally epiphytically, growing on trees, this orchid can bear dozens of 45-cm long spikes, each with over one hundred hyacinth-scented creamy yellow to yellow-green flowers.
Strangely enough, for such a floriferous orchid, the Sydney rock orchid and other varieties of rock orchid are not self-pollinating and produce relatively few seed capsules because they rely on pollinator deception for cross-pollination of their flowers. The Sydney rock orchid produces no nectar reward but relies on the fragrant, musky scent of its hundreds of flowers to attract at least three species of Trigona bee to visit its flowers and while hunting for the nectar that isn’t there, transfer pollinia from flowers of different plants. Fortunately, like most orchids, their relatively rare seed capsules still contain thousands of tiny, windborne seeds, enough to ensure the continued existence of the species for now.
Don’t miss our specimen of Sydney rock orchid in spectacular bloom on your next visit to Flower Dome’s Australian Garden!
Written by: Janelle Jung, Senior Researcher (Research and Horticulture)
A transplanted pake (Hawai'i-born Chinese), she's finding her own Singaporean roots. Every plant has a story, and Janelle helps discover and share these with colleagues and guests, hoping to spark a mutual plant passion! Ask her what plant she named her cat after!