Hyacinth-orchids, Dipodium roseum
Looking like developing asparagus stalks, the hyacinth-orchids have been growing over the last couple of months. Their distinctive pink flower can now been found in almost every section of the Reserve.
There are earlier records of the orchid Dipodium punctatum in the Reserve. Bishop (2000) points out this type was split into new species, one of which was Dipodium roseum. It is the latter species which is currently flowering.
These orchids are thought to be food mimics, attracting native bees for pollination (Weston, Perkins & Entwisle, 2005). The labellum is striped and has a pad of pink/white hairs, both of which point towards the pollinia. The D.roseum can be distinguished from D.punctatum by the degree of curving in the sepals – in the Rosy Hyacinth-orchid, they are strongly reflexed; in the Blotched or Purple Hyacinth-orchid, they are not.
The Rosy Hyacinth-orchid has no leaves and is always found in the vacinity of eucalypts. Whilst they rely on their connection to fungi which form mycorrhiza with eucalypts (probably of the russula kind – see examples of this kind of fungi under ‘gilled agarics’ on our Fungi page)), for sustenance, they are also capable of photosynthesising some of their own supplies. The stems of these orchids are mainly dark purple, although some are green, and this pigment masks the chlorophyll in the stems (Mayfield, 2006).
These will flower into autumn and will then die back to their underground rhizome, sending up shoots again in November.
Sources and other resources
Jones, D.L. (2006) A Complete Guide to Native Orchids of Australia, Reed New Holland: Sydney.
Mayfield, E. (2006) Flora of the Otway Plain & Ranges 1, Linton Press: Geelong.
Weston, P.H., Perkins, A.J. & Entwisle, T.J. (2005) More than symbioses: orchid ecology, with examples from the Sydney Region, Cunninghamia, 9 (1), pp 1–15.