For many with Christmas and New Year holidays it is a busy time but not so with the orchids here in the Adelaide region. The vast majority of orchids have finished flowering for the year except for a few including one of our most showy orchids, the Hyacinth Orchids (Dipodium species). Of the four species found in South Australia, two are found in Adelaide Hills – D. roseum or Common Hyacinth Orchid and D. pardalinum or Small-spotted Hyacinth Orchid and these will be flowering across the whole of the summer period.
Both of these Dipodium species are leafless plants that are dependent upon mycorrhizal fungi associated with stringy bark trees, either Eucalyptus obliqua or E. baxteri. This growth requirement makes it impossible to grow in cultivation. (Stringy bark trees can’t be grown in pots!) The emerging stem and buds resemble an asparagus shoot. The stems can range from a light green through to a deep dark red. At this stage it is difficult to tell the two species apart although if there are yellowing tips on white buds it may be a clue that the plant could be D. pardalinum.
Once in flower D. roseum has a surprising range of variation from carmine (a lightly purplish deep red) through to pink to white, with suffused rather than clearly defined spots. On paler or white flowers these blotches may appear pale mauve-pink rather than candy-pink. It always has a distinctive striped labellum.
This feature sets it apart from D. pardalinum which has a clearly spotted labellum and in contrast to D. roseum, the flowers lack variation of colour but are consistently white with small well-defined candy spots. (There are other Dipodium species with larger spots.)
And the final word, D. roseum is common but D. pardalinum is rated vulnerable in South Australia.
Reference: South Australia’s Native Orchids Bates 2011