Underground orchid  (Rhizanthella slateri)

Listed on Appendix II of CITES (3).

Rhizanthella slateri is the lesser known of the two underground orchid species found in Australia (4). Unlike the western underground orchid (R. gardneri), which never emerges from the soil, the small purple flowers (2) of this species do break through and can be visible amongst the leaf litter on the forest floor (4).

Endemic to Australia, this cryptic orchid has only been observed at a handful of sites in New South Wales and Queensland (2). The discovery in 2002 of a colony comprising around 8 flowering heads on the slopes of Alum Mountain in New South Wales represents the largest population of this species that is currently known (4).

The habitat requirements of this orchid are less understood than those of Rhizanthella gardneri and no particular vegetation type has yet been associated with this species (2).

Very little is known about the ecology of this elusive underground orchid. Flowers are visible on the forest floor in late winter to early spring but further research is needed to determine other factors of its natural history (4).

Rhizanthella slateri is only known from small populations at a few isolated sites, it is therefore at risk from any disturbance to these areas. The recently discovered population close to Buladelah in New South Wales is found on a site that has been designated as part of a highway extension, a development that would result in the loss of this rare orchid (4).

Further research into this underground orchid is desperately needed, both to provide insights into its ecology and to assess its conservation status. It is vital to preserve a meaningful population in the wild if this fascinating species is to persist (4).